Abortion and Stillbirth (new)
Local names: Embua: kuvuna / Luo: tuo bwogo / Kikuyu: muhono, kihuna / Maasai: aibiriu, olik ibiroto / Samburu: ikiboroto / Swahili: homa ya kutupa mamba / Turkana: akiyech / Maragoli: luhusidza / Luvugusu: livure / Nandi: sutonik
Introduction
A very common cause of abortion is Brucellosis, which can also infect humans. Brucellosis is an infectious disease caused by the Brucella bacteria. There are many other infectious abortions. But most labs in the country/region routinely only diagnose few causes of abortion other than Brucella (e.g. caused by bacteria or parasites such as Campylobacter, Trichomonas). However, close observation and submitting a full history together with the samples will help alert the lab on the possible involvement of other abortion agents (e.g. Rift Valley Fever).
Severe general infections of the pregnant dam that cause high fever such as Anaplasmosis, East Coast Fever, Pox and acute Mastitis may also lead to abortion. Sometimes abortion can also have non-infectious causes.
Abortion can occur at very different stages of pregnancy. Very early abortion when the embryo is not yet fully developed and is invisible to the naked eye is called early embryonic death. Most cases of abortion occur later during pregnancy; the foetus looks like a miniature calf but is not developed enough to live. In stillbirth the mother expels a fully developed calf that died before it was born (clear sign: it does not even attempt to breathe).
Single isolated cases of abortion can occur for many reasons and do not always require laboratory diagnosis. But when several animals abort one should consult a veterinarian, laboratory or Animal Health Assistant and request a diagnosis, especially if abortions occur around the same time.
| SPREAD: TO AVOID SPREAD OF ABORTION to other animals the foetus and all abortion/stillbirth materials (incl. liquid) must be removed and disposed of by burning or deep burying (deep enough to protect from dogs and other scavengers). If the abortion has occurred inside a stable the floor must be disinfected. If the stable has a compacted earth floor remove the top layer of the floor and dispose of safely. Immediately separate the abortion animal from the rest of the herd! |
| DANGER: MOST ABORTIONS ARE INFECTIOUS AND VERY DANGEROUS FOR HUMANS. Collecting abortion samples is best done by a veterinarian or an Animal Health Assistant. It is often necessary to also collect a blood sample from the animal that has aborted. When handling the expelled foetus and placenta after an abortion, make sure that you wear plastic gloves and do not touch any of the tissues and liquids with bare hands. If you have accidentally touched abortion materials immediately wash and disinfect your hands. All tissue and samples to be taken to a laboratory must be safely stored in sealed plastic bags with no leakage (use double plastic bags or put plastic bags in a waterproof container). |
General warning:
Retained placenta is common after the abortion and often requires antibiotic treatment. Trying to forcibly remove the placenta without protective gloves and clothing exposes humans to severe infection risks and may also harm the animal. Do not foster calves, kids or lambs onto dams which have aborted!
Milk from aborted animals is very often highly infectious for the young suckling animals and for humans.
Abortion organisms are mostly spread via uterine discharges, the afterbirth and the expelled foetus at abortion. Removing and burying or burning abortion materials from the stable or the Boma will prevent the organisms from infecting more pregnant animals. It is also important to disinfect the place where the abortion happened. Never touch abortion materials directly with your bare hands, always use protective gloves.
There are many different names for abortion in local languages:
Embua: kuvuna / Luo: tuo bwogo / Kikuyu: muhono, kihuna / Maasai: aibiriu, olik ibiroto / Samburu: ikiboroto / Swahili: homa ya kutupa mamba / Turkana: akiyech / Maragoli: luhusidza / Luvugusu: livure / Nandi: sutonik /
Diagnosis
Diagnosis of abortion requires professional help and laboratory examination. When you think there is an abortion problem consult a veterinarian/VO/DVO.
Laboratory diagnosis of abortion in livestock can be difficult and is not always successful. Often the aborted foetus is too decomposed or too contaminated to allow for a diagnosis. Toxic or genetic causes of abortion are very difficult to diagnose in the lab.
To confirm the presence of a particular abortion agent in a herd two blood samples should be taken from 10% of the animals that have aborted (2nd sample to be collected 2-3 weeks after 1st sample). - In lactating cattle Brucellosis can also be diagnosed from milk (see under Brucellosis).
Abortions Caused by Bacteria: Brucellosis, Salmonella, Leptospirosis, Vibriosis
Brucellosis
For complete description on Brucellosis click here.
Summary
In some countries Brucellosis has been eradicated or brought under control by a programe of blood testing, slaughter and heifer vaccination. However in most parts of East Africa there has been no control or vaccination and Brucellosis is common in both humans and animals.
Brucellosis in humans resemble Malaria, and is often mistaken as such unless identified through laboratory testing. Cure of Brucellosis in humans is a very long drawn out and expensive administration of antibiotics and much better avoided by controlling the disease in livestock.
In livestock it is not possible to treat Brucellosis. However, some cattle resist infection and a small percentage of infected cows spontaneously recover.
Cattle/sheep/goats/pigs and camels/donkeys become infected by eating the organism from abortion material, genital discharges, or contaminated pasture, food or water. Abortion occurs 2 weeks to 5 months after the initial infection and generally occurs after the 6th month of pregnancy.
Abortion due to Brucella mostly occurs during the last third of pregnancy. In unprotected herds 40% to 80% of pregnant females may abort or give birth to very weak newborns. After abortion animals give no or only little milk.
Brucellosis is often present in the raw milk, which presents a serious risk to human health as this is a dangerous zoonosis. Always boil milk before consumption!
Signs of Brucellosis
- Abortion is the most obvious manifestation. Animals abort from the 7th month onwards.
- Infections may also cause still births or weak calves, retained placentas, and reduced milk yield. Usually general health is not affected in uncomplicated abortions.
- In less acute (insert dictionary) infections, cattle may give birth to a full term but weak calf, or merely show a retained placenta. Cows may become infertile due to chronic (insert dictionary) uterine infection.
- After abortion, the afterbirth doesn't come out (retained placenta). This can further develop to Mmetritis (infection of the uterus), which often causes infertility.
- In bulls, no symptoms may be seen but if they are, they may include inflammation of the testes, lack of sexual activity and possibly infertility.
- Subcutaneous (under the skin) swellings containing infected fluid may appear on the legs of infected cattle and the placenta often has a thickened leathery appearance with some discolouring
- Infections may also cause still births or weak calves, retained placentas, and reduced milk yield. Usually general health is not affected in uncomplicated abortions.
- In less acute (insert dictionary) infections, cattle may give birth to a full term but weak calf, or merely show a retained placenta. Cows may become infertile due to chronic (insert dictionary) uterine infection.
- After abortion, the afterbirth doesn't come out (retained placenta). This can further develop to Mmetritis (infection of the uterus), which often causes infertility.
- In bulls, no symptoms may be seen but if they are, they may include inflammation of the testes, lack of sexual activity and possibly infertility.
- Subcutaneous (under the skin) swellings containing infected fluid may appear on the legs of infected cattle and the placenta often has a thickened leathery appearance with some discolouring
Prevention of Brucellosis
A single vaccination of all female animals between 5 and 8 months of age with S19 vaccine will give adequate immunity for the lifetime of the livestock. Adult vaccination should be avoided if possible to allow serum sampling in an outbreak of abortions to be interpreted without the confusion caused by antibodies due to vaccination with the live S19 vaccine.
Salmonella species
For further information on Diarrhea of the young see here
Salmonella can cause disease in livestock and in humans. They cause diarrhoea and death in young suckling animals, but also diarrhoea and abortion in adult animals. In many countries Salmonella dublin is endemic in cattle and is the most common type of Salmonella causing abortions. Many other Salmonella types may be involved in individual cases. Salmonella also cause disease and abortion in sheep, goats and camels. Aborting animals may have fever and diarrhoea or show no symptoms other than abortion.
Salmonella are also very common causes of diarrhoea in young animals and chicken and can even infect eggs. Humans can get food poisoning from handling raw chicken meat and from consuming raw or undercooked eggs.
All types of Salmonella are zoonotic, they can cause infections and food poisoning in humans.
Abortion due to Salmonella may occur at any time, but is seen mostly during the last third of pregnancy (in cattle between 6 and 9 months).
No specific lesions are seen in the placenta or the foetus.
Leptospirosis
This infection is a problem especially in cattle. Up to 30% of a dairy herd may abort during an outbreak of Leptospirosis. The disease is zoonotic. Leptospirosis infections in humans happen when humans come into contact with infected animals, urine, contaminated water, infected carcases or drink infected milk. In humans Leptospirosis varies, it may be mild, severe or even cause death.
Sorurces of infection:
- Rodents act as carriers and are a source of infection
- Watercourses and standing and stagnant water (e.g. on very wet pastures) can become contaminated and be a source of infection.
- Sheep and goats may be "silent" carriers and a potential source of infection for cattle and humans.
- The infection may be transmitted via urine, milk, abortion material and during mating
Leptospira cause abortions in the last third of pregnancy. Outbreaks are more common when the weather is wet and there is standing water that is contaminated with infective organisms.
Symptoms of Leptospirosis
Cattle may abort without symptoms of illness, or may be acutely ill with severe jaundice (yellowing of gums and white of eyes), fever, haemoglobinuria, photosensitzation (for further information on photosenzitation see here), and in some cases even death.
For more information please also see Leptospirosis under zoonotic diseases
The aborted placenta is yellow-brown and swollen
The foetus usually dies 1-2 days before expulsion and so is already decomposed.
Prevention by:
- Where the vaccine is available, vaccination with a multi-valent Leptospirosis vaccine, every 6 months is recommended.
- Avoid or drain pastures with standing water.
- Sources of infection, such as contaminated water and feed should be identified and eliminated
- Rodents and other vermin should be destroyed. It should be noted that cattle may be life-long carriers of leptospirosis and remain a source of infection.
Diagnosis from Laboratory:
Diagnosis of Leptospirosis is very difficult and only performed by specialized labs. Diagnosis can be made from the foetus organs and the mothers? urine and blood.
A combination of very wet pastures, abortions and jaundice in cattle, occasionally also skin problems is suggestive of Leptospirosis. Abundance of rodents in stables/barns/pastures strengthens this suspicion.
A combination of very wet pastures, abortions and jaundice in cattle, occasionally also skin problems is suggestive of Leptospirosis. Abundance of rodents in stables/barns/pastures strengthens this suspicion.
Campylobacter (also called Vibriosis)
For further information see under Birth and Reproduction problems
Scientific name: Campylobacter fetus venerealis and Campylobacter fetus fetus
Common names: Bovine campylobacteriosis, Genital vibriosis
This infection is a problem in cattle and sheep. Campylobacter bacteria cause early embryonic death, infertility and occasionally abortion. This is a venereal disease transmitted during mating. Infected bulls are the source of infection and most outbreaks occur after the introduction of an infected bull into a clean herd. Vibriosis is not zoonotic
- Most cases of abortion occur between 4 - 8 months of pregnancy.
- Usually there are no significant findings other than a mild inflammation of the placenta.
- Diagnosis in the lab is very difficult. Bulls penis sheath washing transported to the lab within 6-8 hours are useful for identification of infection.
- Vibriosis in sheep is evidenced by abortions in late pregnancy and stillbirths
Mode of spread
In cattle the disease is transmitted during mating. It is also transmitted by contaminated instruments, bedding or by artificial insemination using contaminated semen. Individual bulls vary in their susceptibility to infection. Some become permanent carriers, while others appear to be resistant to infection. In young bulls, less than 3-4 years of age, infection tends to be temporary, with transmission apparently relying on sexual contact with a non-infected cow within minutes to days of breeding with an infected cow. Spontaneous clearance in these younger bulls does not seem to be related to any immune response and so re-infection can readily occur. Bulls older then 3-4 years are more likely to suffer chronic infections.
Some cows clear the infection rapidly; others carry it for up to or longer than 2 years. Although most of the genital tract may be free of infection, when a cow eventually conceives the vagina may remain chronically infected throughout pregnancy.
Some infected females can maintain pregnancy but abort usually around the fifth month of pregnancy or sometimes earlier. This means that the presence of the disease can go un-noticed without proper herd fertility records. Breeding females eventually eliminate the infection six months after being infected at service and recover completely. They are then immune and can breed normally.
Signs of Vibriosis
Vibriosis affects both breeding males and females but clinical sings of temporary infertility are confined to females. Clinical signs, other than reproductive failure or abortion, are minimal or absent. The infection of females at conception results in infection in the anterior vagina which subsequently spread to the uterus and fallopian tubes. The infection persists for months and causes the developing foetus to die. The embryonic death initiates cyclical activity in the ovary but these cycles are often irregular with prolonged intervals. Observed abortions are uncommon.
Clinical signs in herds for which good records are maintained are soon evident shortly after the introduction of an infected bull. Animals which have been presumed to have been in calf have irregular returns to heat. In more extensive systems using natural service infection may not be suspected until the calving pattern indicates a delay in conception and a reduced calf crop.
Where the disease has been present for some time indications that C. fetus is present may be much less dramatic, with only heifers, calved heifers and a few susceptible cows being affected, as older animals have acquired natural immunity.
Bulls show no symptoms and produce normal semen. In other words they are fertile, mate normally, and provided they do not have to serve too many returning females, active. The females they serve conceive, but they have been infected. Subsequently the foetus dies and they return to service.
The disease in sheep manifests with abortions in late pregnancy and stillbirths. Ewes may develop inflammation of the uterus after expelling the foetus, which is usually rotten, with 40% having orange-yellow spots in the liver. The disease in sheep is acquired by mouth, not via the ram.
Diagnosis
This would be based on the history of late abortions and return to heat after successful mating.
Laboratory diagnosis is based on the vaginal mucus agglutination test. Samples are taken from at least 10% of the herd, concentrating on those females most recently exposed to infection by service, open cows or those returning to their third or fourth service. Tampons are placed in the anterior vagina and sheath washings are taken from suspected bulls.
Diagnosis in sheep depends on finding the organism in the stomach, placenta or uterine discharge.
Prevention
Use of Artificial Insemination with semen from non-infected bulls should eliminate the infection from an infected herd within two complete breeding cycles.
Care must be taken when buying breeding bulls. A veterinary certificate stating that they are free of Vibriosis (and Trichomoniasis) should be insisted upon.
Where AI is not feasible, all animals in a herd should be tested and the infected and non-infected animals managed separately. This approach requires a high level of management and careful veterinary supervision.
Vaccination is practiced where the vaccine is available.
In sheep strict hygiene and regular vaccination, where the vaccine is available, should be practiced.
Control is by:
- Vaccination
- Replacing natural mating by artificial insemination until all cows have had two pregnancies.
- The infected bull may be treated with Streptomycin injection combined with oil-based Streptomycin applied locally to the penis is possible. This treatment must be carried out on 3 consecutive days and should be applied by a trained professional. Bulls are of course susceptible to re-infection if they mate with an infected female.
- It is not necessary to treat infected cows, they generally recover spontaneously.
- In sheep the use of tetracyclines may help to prevent exposed ewes from aborting.
Abortions and infertility in cows caused by Vibriosis look exactly as those due to Trichomonas (see under Trichomonas).
Abortions Caused by Bacteria: Listeriosis, EAE, Q-Fever
Listeriosis
Listeriosis is a zoonosis and may spread to people via raw milk, it can cause severe infections that can sometimes lead to death.
The organism Listeria is widespread in the environment being present in the soil, sewage effluent, bedding and feedstuffs (especially poor quality silage). Cattle, sheep and goats get the disease by eating infected feedstuff. Sheep and goat are more susceptible to Listeriosis than cattle. The infection then travels to the placenta, causing inflammation.
Many outbreaks are associated with the feeding of poor quality silage, especially if the silage contains soil.
Signs of Listeriosis:
- Central nervous symptoms (Encephalitis, e.g. one ear hanging down) and sometimes eye infections.
- Sporadic abortion, the foetus is usually decomposed when aborted.
- The placenta is inflamed with multiple, yellow or gray coloured spots in the cotyledons; similar spots are found in the liver of the aborted foetus.
Abortion usually occurs in late gestation and is usually sporadic, although rarely abortion storms may occur.
There is no vaccine. Although antibiotics have an effect on Listeria, the cure rate after injecting antibiotics is very poor. Animals that do recover and return to feeding often still show some nervous symptoms. Control should involve an awareness of the risks of feeding poor quality silage contaminated by soil.
Enzootic Abortion of Ewes (EAE)
This disease can be a big problem in sheep and goats. It is caused by a bacterium called Chlamydia (old name) or Chlamydophila (new name), which can cause sporadic abortion in cattle and also infects people.
Infection is via feeding in a contaminated environment. During the next pregnancy the organism invades the placenta and causes abortion.
If rams are infected, they may develop inflammation of the testicles and the organism is excreted in the semen, but spread by the ram does not play a role.
Signs of Enzooic Abortion
Abortion storms, involving up to 30% of ewes in a flock, are a feature of EAE, especially in intensively managed flocks. Ewes are not noticeably ill. They abort only once from EAE and have solid immunity after the abortion.
Abortions occur in the last three weeks of pregnancy and weak, live lambs may be born alongside dead lambs.
The placenta between the cotyledons is thickened with a brownish colour over the surface. The foetuses are usually fresh.
The organism is present in large numbers in the abortion products and vaginal fluids for up to three weeks after the abortion, leading to heavy contamination of the environment and infection of other sheep. Some ewes can become permanent carriers of the infection.
Diagnosis
Examination of fresh placenta is the method of choice for the diagnosis of EAE, but make sure to use gloves!! Alternatively, vaginal swabs or swabs taken from the coat of aborted foetuses can be used.
Prevention and Control
Various vaccines are available, including an inactivated vaccine for use in pregnant animals, but they are not marketed in Kenya / East Africa.
In the face of an outbreak, mark and isolate aborting ewes, dispose of bedding and abortion products and disinfect pens. Ewes that have aborted should not be used to foster lambs.
| WARNING: Pregnant women should NOT deal with lambing ewes and goats or any aborted material from sheep and goats. Many infections, which cause abortion in sheep and goats, are transmissible to humans. Especially the agent of EAE( Chlamydophila) is capable of causing severe disease and abortion in pregnant women. - Toxoplasma, Q-Fever, Salmonella, Leptospira and Listeria can also cause disease and abortion in humans |
Q-Fever Coxiella burnetii
Q-Fever was first identified in Queensland, Australia; hence its name.
This is a bacterial disease, and an important zoonosis (an animal disease that can be transmitted to humans). Q-Fever is caused by an organism called Coxiella burnetii. It is found all over the world, in every country where it has been sought.
Its main importance is its ability to infect man, and to cause a severe respiratory disease. In ruminant livestock Q-Fever leads to abortions, inflammation of the lining of the uterus and mastitis.
Q-Fever is a disease passed to humans from sheep. People working around domestic sheep should consider getting vaccinated against this disease. The disease can be acquired from the inhalation of aerosolized barnyard dust should it contain infected dried urine, manure particles, or dried fluids from the birth of calves, or lambs, or raw milk.
Coxiella burnetii is an extremely difficult organism to eliminate. It is very tough, resisting most disinfectants, heat and drying, and surviving for years in dust.
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| View of a larval Ixodide, Dermacentor marginatus[I/] hard tick. This tick species is known to be a vector for Q-fever, which is caused by the bacteria Coxiella burnetii[I/]. |
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(c) Picture from CDC/Donated by the World Health Organization, Geneva, Switzerland
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Mode of spread
There are two different cycles:
1. The bacterium cycles between small free-living ground mammals and ticks
2. The bacterium cycles in domestic ruminants (cattle, sheep, goats), independent of the wild animal cycle , ruminants infect each other via abortion fluids and abortion materials that contaminate stables and pastures
Ticks can act as reservoirs of the Q-Fever organism. Tick-free cycles in domestic ruminants allow the organism to be concentrated in the genital tract and udder, from where large numbers are shed in milk, faeces or urine, or, from the genital tract at lambing or calving.
A wide variety of other animals and birds may also be infected and play a part in spreading Coxiella burnetii. These include dogs and several species of birds.
At-risk animals, and man, become infected by inhaling infected fluid discharges in the air or dust loaded with dried discharges.
The disease is highly infectious. Animal handlers are particularly at risk from infection, especially at lambing or calving, from inhalation, ingestion or direct contact with birth fluids or afterbirth.
However the main route of most human infections is by inhalation of contaminated air droplets or dust originating in infected ruminants or other animals e.g. cats.
Spread can occur up to 10 kilometres from the source of infection by wind dispersal of dried reproductive products, such as afterbirth, genital discharges, etc. from infected sheep, cattle and goats, depending on wind condition.
Symptoms of Q Fever
Infection in ruminants is usually symptom-free, but it can cause late abortions, inflammation of the uterus and mastitis in sheep and goats, together with loss of appetite, and offspring of carrier animals can often appear weak, showing low vitality. Large numbers of organisms are shed in the milk, urine, faeces, saliva and especially through the afterbirth and uterine discharges. These are the main sources of infection for man. Cows may shed the organism in milk for years.
Symptoms of Q- Fever in man can easily be mistaken for those of flu: fever, headache, chills, muscle pains, lack of appetite and nausea. The incubation period is about 2 to 3 weeks, and the disease lasts for 1-2 weeks.
In severe and chronic cases, pneumonia, hepatitis and endocarditis may occur and in some cases the infection causes death, as has happened in the recent outbreak in north-west Europe.
The infection of pregnant women can result in abortion or premature delivery.
The main route of infection is by inhalation of infected dust or aerosol droplets. Drinking contaminated raw milk products in unlikely to cause any symptoms of disease.
Diagnosis
There are no clinical signs in domesticated animals. The sudden appearance of an influenza-like disease in man following an association with cattle, sheep or goats, or with their carcases, hides, tissues, or following an autopsy, should be regarded as evidence of infection.
But neither the history nor the clinical picture is enough to prove the presence of Q Fever. A definite diagnosis can be established only by lab tests to identify the bacteria that causes the disease in the blood or sputum of a patient.
Other causes of abortion in ruminants should be considered when reaching a diagnosis.
Control
Recovered animals remain infected and infective for many years and sometimes for life. It is therefore necessary to take steps to limit the spread of infection by adopting hygienic precautions at the time of lambing, kidding and calving. In particular afterbirths should be destroyed. In known infected flocks or herds pregnant animals should be separated from others indoors.
Vaccines are available and are being developed in Europe and when given to uninfected animals have prevented infection. When given to previously infected animals the vaccines have improved fertility and reduced the shedding of organisms.
This disease is probably much more common than is realized, due to under reporting and lack of facilities in reaching a diagnosis.
Treatment
In animals this is seldom attempted. Oral tetracyclines (antibiotics) are reported to have a beneficial effect, but their use carries risks in ruminating animals such as cows, and is therefore not recommended.
Viral Causes: BVD, Border disease, Infectious Bovine Rhinotracheitis, Rift Valley Fever
Bovine Viral Diarrhoea (BVD)
This virus is also an important cause of diarrhea. For more information Link to Diarrhea of adults
This infection is a problem in cattle. BVD is the most commonly diagnosed virus in bovine abortion cases in Europe and North America.
The virus can cause:
- Early embryonic death
- Mummification of the foetus
- Abortion
- Stillbirth
- Birth of calves with congenital defects of the eye/brain
- Birth of weak calves that do not thrive, even if they reach adulthood
Persistently infected animal are the source of infection for susceptible animals. Some persistently infected animals die early, others live long enough to join the adult herd and produce persistently infected calves.
Diagnosis is established through blood tests.
Prevention focuses on the removal of infected animals and herd vaccination. There are live virus vaccines and inactivated viral vaccines. The latter should be used in pregnant cattle.
Border Disease
This disease only affects sheep. It is caused by a virus related to the one that causes Bovine Viral Diarrhea disease in cattle. (For more information please Link to Diarrhea of adults)
The virus usually enters a flock through the purchase of a persistently infected sheep. Problems are seen at the next lambing, i.e. barren ewes, stillbirths, abortions and persistently infected lambs which will continue to act as a source of infection for the rest of the flock. Permanently infected sheep that reach breeding age may have reduced fertility and can either abort or produce live permanently infected lambs.
Signs of border disease
In non-pregnant sheep the infection is inapparent, leading to long-lived immunity.
- Early foetal death with subsequent resorption (only sign: lot of barren ewes)
- Mummification, abortion or stillbirth.
- Birth of the so-called 'hairy shaker' lambs, with coarse wool over the head and neck, permanent trembling, and an abnormal skeleton. They show very poor growth rate.
Diagnosis
This is possible on samples of blood and brain tissue.
Prevention and Control
Prevention is achieved by operating a closed flock system and testing all replacements. As there is no local laboratory capable of testing for presence border disease, any system here must depend on close observation. If ?hairy shaker? lambs are born in large numbers, then segregate in-lamb ewes from those with affected lambs and, as infection during pregnancy results in an immunity to re-infection, mix susceptible animals retained for breeding with surviving hairy shakers through the grazing period to maximize their chances of becoming immune.
There ie is no vaccine.
Infectious Bovine Rhinotracheitis
(For more information please see also under Respiratory diseases)
This infection is a problem in cattle. The disease is caused by a herpes virus and usually results in respiratory disease, but may also cause sporadic abortions in cows. Abortions generally occur in late pregnancy and aborting cows may or may not have shown respiratory signs previously. When there is a high fever resulting from systemic or respiratory disease this can also cause abortion.
Cows may be carriers of the virus.
Control is by herd vaccination and intranasal, modified live virus and killed vaccines are available.
Rift Valley Fever
Introduction
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| Aborted foetus after Rift Valley Fever |
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(c) USDA
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Rift Valley Fever (RVF) is an acute mosquito-borne viral disease affecting domestic ruminants (cattle, sheep, goats, camels, domestic buffaloes) and man. It occurs mainly in Eastern and Southern Africa. Outbreaks have also occurred in Egypt, West-Africa (Mauretania), Saudi Arabia and Yemen. During epidemics the sudden occurrence of mass abortions at all stages of pregnancy especially in sheep and camels, deaths in new-born animals and severe influenza like occasionally also fatal haemorrhagic disease in humans are characteristic. Apart from Rabies, RVF is probably the most deadly zoonotic disease transmitted from animal to man. RVF outbreaks in Eastern Africa, including Somalia, have caused hundreds of deaths in humans.
Formerly, apart from mass abortions, most cases in adult animals were mild, but in recent times a haemorrhagic form of the disease has emerged with rapid death in mature animals, including even cattle.
There is a remarkable age-related innate resistance to RVF virus; mortality rate in lambs less than 1 week old exceeds 90% whereas the rate in lambs over 1 week drops to 20%.
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| Widespread flooding causing mosquito eggs to hatch |
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(c) F. Glyn Davies
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Major RVF outbreaks in animals and humans occur in 5 to 20 year cycles. Between epidemics, the virus survives in mosquito eggs laid on vegetation at the edge of flood zones When these are flooded the eggs hatch. This only occurs when the water table rises following prolonged and very heavy rain, for example during El-Nino. The mosquitoes hatch in massive numbers and start infecting livestock.
Mode of spread
Epidemics in domesticated animals are started by the bites of infected mosquitoes. After this, infective droplets generated by aborted foetuses and abortion fluids spread the disease rapidly through the flock or herd.
Humans are usually infected by inhaling infectious droplets when handling infected animals or tissues (meat!) or abortion materials. This occurs when slaughtering animals during a RVF outbreak and when assisting infected animals during abortion. Until recently the disease in man was considered to be a non-serious influenza type illness, but a fatal haemorrhagic form has emerged and now RVF in man is considered to be one of the most dangerous diseases known.
The virus may spread over large areas by windborne mosquitoes and also through movement of infected animals.
Signs of Rift Valley Fever
- The incubation period in lambs is 12 to 36 hours. A fever of up to 41degC (106degF) may develop.
- Peracute infections occur in new-born lambs which die within hours. Acute reactions occur in older lambs and calves and occasionally in adult sheep.
- In very severe infection in calves, death may occur in 2 days after infection without their showing any clinical signs.
- A haemorrhagic syndrome was observed during the last outbreak in Kenya, affecting adult cattle.
- In its severe form, calves will develop high fever, and may vomit. Some nasal discharge may also be seen followed by prostration and mortality may reach up to 70%.
- Almost all infected pregnant sheep and camels abort within a short period and at very different stages of pregnancy. Cattle are more resistant but may also abort.
- Subacute reactions occur in adult sheep, cattle and camels. There is a low-grade fever, partial lack of appetite and general weakness. Jaundice is prominent and foul smelling diarrhoea can occur.
- In pregnant ewes the mortality and abortion rates varies from 5 - 100%. Abortion rates in pregnant camels are between 80% and 100%
Diagnosis
When suspecting RVF do not touch abortion materials, keep a distance from aborting animals, do not attempt any post-mortems and stop all slaughter of animals for meat. Blood tests are used to confirm a RVF diagnosis. The DVO or vet department should immediately be alerted when unusually high numbers of abortions occur soon after strong rainfall and flooding.
In sick humans, there is a lack of appetite, nausea, severe headache, joint pains, dizziness and nose bleeding. Encephalitis, retinitis, photophobia, loss of central vision, irritation, stupor and coma can occur. Haemorrhagic RVF is characterised by a very acute febrile illness, accompanied by jaundice. Widespread haemorrhages develop within 2-4 days and death usually occurs within another 3-6 days. There is no treatment for RVF in livestock and humans. Patients who are immune-suppressed or malnourished are at particular risk of death.
Recovery from RVF is followed by lifelong immunity.
Prevention and Control
- Outbreaks of Rift Valley Fever generally occur after periods of prolonged and very heavy rain. Such being the case livestock owners should be aware that if long rains are excessively heavy and cause widespread flooding, an outbreak of Rift Valley Fever is likely to occur.
- Control of mosquitoes through use of insecticides, acaricides and pour-ons, movement of stock to dry areas or to higher cooler altitudes can all help in preventing the RVF outbreak from reaching your herd.
- Immunisation remains the only effective way to protect livestock but vaccination of animals with suitable RVF vaccines can only be carried out under authority of the DVS by government veterinary vaccination teams. Some live RVF vaccines can also cause abortions and should NOT be used in pregnant animals.
Treatment
There is no known medical treatment for Rift Valley Fever.
Fungal Causes
Fungi cause sporadic abortions. The abortion occurs from mid to late pregnancy.
Mouldy hay, straw, silage and brewer's grains used as feed or as bedding are the most important sources of infection. Fungi are inhaled and travel via the bloodstream to the placenta. Grey ringworm-like lesions may be seen on the head and shoulders of the foetus, which is not usually decomposed when it is expelled.
Diagnosis is based on isolation of fungi from the foetal stomach, placenta and skin lesions.
The only prophylaxis is strict avoidance of mouldy feed and bedding.
Protozoal Causes: Neospora caninum and Trichosomiasis
Neospora caninum
This parasite which is harboured by dogs occurs worldwide and is a common cause of abortion in dairy cattle; it also occurs in Kenya/East Africa. - Pups born from infected dogs show signs of paralysis.
In cattle sporadic abortion most commonly occurs between 4 and 6 months of gestation. Abortion storms have been observed and repeat abortions in affected cows have also been reported. Stillbirth can also occur. Occasionally infected calves are born alive; they are underweight, weak and often show signs of paralysis. Sometimes the paralysis develops as late as 4 weeks after birth. - Usually the aborted foetus is decomposed, cows are not clinically ill and the placenta is not retained.
Transmission to cattle is via feed contaminated with dog faeces. Transmission from cow to cow does not occur.
There is no safe treatment and no vaccine.
Strict hygiene to prevent contamination of feed by dogs' faeces is the only prevention. Strictly keep dogs out of feeding areas and pastures.
Trichomonas fetus (Trichomoniasis)
Trichomoniasis is a venereal protozoal infection of cattle caused by Trichomonas foetus. It occurs without fever and is contagious. Trichomoniasis is confined to the reproductive tract of the cow and the penis sheath of the bull. The disease occurs worldwide.
Mode of spread
The infection is spread through mating or through the use of contaminated insemination instruments or stockmen's hands.
T. foetus infection is confined to the reproductive tract, where it can invade most parts. Infection normally lasts about 3 months. There is usually a mild inflammation of the vagina shortly after infection but significant changes do not normally take place until 50-60 days after infection when strong inflammation of the vagina and uterus, accumulation of pus in the uterus and early abortion may take place.
Abortions are often undetected and the main feature observed is often a failure of cows to hold to service.
Infection in the male is usually confined to the surface of the prepuce and penis and is usually so mild it is not clinically apparent.
Signs of Trichomoniasis
- Cows may have a more than normal watery vaginal discharge about 2 weeks after coital infection
- Abortion may occur in early or late in pregnancy
- After abortion the placenta is often retained and there may be pus in the uterus.
- The foetus has no specific lesions.
- Inflammation of the uterus and pyometra ? a pus filled uterus
- There is irregular heat and the cow may stop coming into heat altogether
- Cows eventually clear themselves of infection and the uterus is usually normal 2-6 months after infection
Bulls show no symptoms but once infected tend to remain permanent carriers.
Diagnosis
Trichomoniasis can be suspected in any breeding cattle if there is a history of reproductive failure characterized by repeated returns to service, a lower than expected pregnancy rate, a wide range of gestational ages and cases of early abortion and pyometra.
Laboratory diagnosis is possible and can be made from a foetus, placental fluids, uterine contents, or via mucus taken from the vagina or from sheath washings from carrier bulls.
Diseases with similar symptoms
The disease must be differentiated from Vibriosis which it resembles.
Prevention and Control
The simplest control method involves ceasing to breed cows for at least 3 months, by which time they will have eliminated the infection, and to carry out examination of the cervical mucus using the vaginal mucus agglutination test.
Use of a clean bull either for natural mating or artificial insemination is also a control method.
Recommended treatment
The majority of infected cows and heifers recover completely and clear the infection and so they are not normally treated.
In bulls treatment using various Imidazoles has been used but none is both safe and effective. Ipronidazole is probably the most effective but can cause sterile abscesses at the injection site. In addition bulls are probably susceptible to re-infection after successful treatment.
Resistance to Ipronidazole may also be a concern. The biggest problem, however, is that the success of treatment is measured by repeat sampling which may mean that the individual bull can never be definitely said to be negative. Therefore it is better to slaughter the bulls and replace them with virgin bulls or to test and cull positive bulls.
Re-infection is prevented by exposing only uninfected (clean) bulls to uninfected (clean) cows. Clean cows are assumed to be those with calves at foot and virgin heifers.
Non-infectious Causes of Abortion
In most cases, without a good history and physical examination of the aborting animal it is not possible to diagnose non-infectious causes of abortion in the laboratory.
Physical
Abortion may be caused by trauma (shock/sickness), high fever of the pregnant mother or accidental insemination of pregnant animals. The foetus is well protected by its surrounding of amniotic fluid so factors like high environmental temperatures and being pressed in a crush are not likely to cause abortion.
Nutritional deficiencies
- Iodine deficiency has been associated with stillbirths and weak newborn calves. Lack of Iodine in the soil is known for certain areas of Kenya /East Africa
- Feeding of kale to livestock.
- Application of human sewage sludge to pasture.
- Selenium/Vitamin E deficiency has been associated with bovine abortions, soils in some parts of Kenya are Selenium deficient.
- Vitamin A deficiency, which can occur towards end of the dry period and during drought, may also interfere with pregnancy.
Toxic (poisons)
Various toxins, such as those which occur in a number of plants, may cause abortion.
Cattle frequently abort following an outbreak of nitrate/nitrite poisoning (after heavy fertilization of pastures with nitrogen fertilizer) which poisons the dam and subsequently also the foetus. Common sources of nitrate/nitrite on farms are commercial fertilizers but also certain plants
.
Signs of nitrate/nitrite poisoning
- Severe difficulty in breathing,
- Muscle twitching
- Brown mucous membranes and blood are likely to be present
Genetic
Genetic abnormalities may result from high levels of inbreeding in the herd. Signs are congenital malformations, foetal death and abortion. Bulldog calves are one example. To prevent such genetic problems inbreeding should be avoided.
Review Process
1. William Ayako, KARI Naivasha. Aug -Dec 2009
2. Hugh Cran, Practicing Veterinarian Nakuru. March ? Oct 2010
3. Review workshop team. Nov 2 - 5, 2010
- For Infonet: Anne, Dr Hugh Cran
- For KARI: William Ayako - Animal scientist, KARI Naivasha
- For DVS: Dr Josphat Muema - Dvo Isiolo, Dr Charity Nguyo - Kabete Extension Division, Mr Patrick Muthui - Senior Livestock Health Assistant Isiolo, Ms Emmah Njeri Njoroge - Senior Livestock Health Assistant Machakos
- Pastoralists: Dr Ezra Saitoti Kotonto - Private practitioner, Abdi Gollo H.O.D. Segera Ranch
- Farmers: Benson Chege Kuria and Francis Maina Gilgil and John Mutisya Machakos
- Language and format: Carol Gachiengo
4. Updating by Dr Hugh Cran, Practicing Veterinarian, Nakuru, Kenya, Sept 2011
5. Reorganising, review and updating May 2013 by: Dr Mario Younan (DVM, PhD), Regional Technical Advisor for VSF-Germany, working in East Africa since 1995
Information Source Links
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- Cabell, Emma 2007: In Practice Journal of Veterinary Postgraduate Clinical Study Volume 29 No 8 September 2007. Abortion in Cattle: causes and investigation ISSN no 0263/841 X
- Force, B. (1999). Where there is no Vet. CTA, Wageningen, The Netherlands. ISBN 978-0333-58899-4
- Handbook on Animal Diseases in the Tropics 4th Edition Sewell & Brocklesby
- Henning MW (1956): Animal Diseases in South Africa, 3rd Edition. Onderstepoort Veterinary Institute, Central News Agency Ltd., Pretoria, South Africa
- Hunter, A. (1996). Animal health: General principles. Volume 1(Tropical Agriculturalist) - Macmillan Education Press. ISBN: 0333612027
- Khan CM and Line S (2005): The Merck Veterinary Manual, 9th Edition, Merck & Co Inc Whitehouse Station NJ USA. ISBN 0-7020-1502-4
- Martin W B 1983 (Editor):Diseases of Sheep ISBN 0- 632- 01008-8
- Pritchard Geoff 1990: Diagnosing the cause of bovine abortion. In Practice Journal of Veterinary Postgraduate Clinical Study Volume 12 no 3 May 1990 ISSN No 02 63/841 X
- Q Fever booklet, CEVA Sante Animal, France
- lowey, R.W. (1986). A Veterinary book for dairy farmers: Farming press limited Wharfedale road, Ipswich, Suffolk IPI 4LG