Enzootic abortion may occur at any stage of pregnancy that usually results in stillbirths. However, some fetuses are born alive but weak, and they are most likely to die after a few days.
It has been suggested that the most prominent cause of abortion after three months of pregnancy is due to nutritional energy deficiency. Other infectious diseases that may cause abortions in ewes include Rift Valley Fever, Wesselsbron, Coxiella (Q-fever), Campylobacter, rarely Brucellosis (meletensis) or Border disease.
Enzootic abortion outbreaks are usually prevalent after one to two years when new sheep or goats are introduced to a flock.
Causes of enzootic abortion
This disease is caused by a pathogen known as Chlamydia psittaci. This infection is one of the leading causes of stillbirths and abortion in ewes and nannies. This disease is prevalent all around the world, affecting many species, such as birds, cattle, and humans.
Other diseases are also linked to this disease, and they include digestive tract and respiratory tract infections.
Symptoms of enzootic abortion
Although there are no significant clinical signs in infected ewes, abortions usually occur during the last month of pregnancy. However, it can occur as early as three months into pregnancy. When abortion happens that early, the dead fetus is reabsorbed instead of removed from the body.
The farmers suffer low lambing and weaning rate. Asides from abortions, infected ewes are delivered from weak lambs. Most of these weak lambs die after a few days of being born while the surviving ones remain infected.
There is about seventy per cent of abortion cases when a flock is infected for the first time. However, the rate is likely to drop because the same ewe has fewer chances of having an abortion again. During an outbreak in contaminated farms, abortion is often observed in maiden ewes.
Chlamydia psittaci can cause the following disease conditions:
- Placentitis, foetal death, and abortion
- Enteritis (diarrhoea)
- Polyarthritis (lameness)
- Epididymitis, orchitis, seminal vesiculitis
How is enzootic disorder spread?
Outbreaks are normally noticed after the introduction of new sheep or goats into a flock. This livestock might be infected, and mixing them up with healthy animals in your flock will encourage the spread of the disease. This is because, during lambing time, an infected ewe can infect another.
Also, vaginal discharge, uterine fluid, and faeces of an infected ewe can contaminate the pasture, which makes it easier to infect a healthy animal. This disease can also be sexually transmitted and can occur when rams (that are carriers of the pathogen) transmit it through their semen.
This infection can stay dormant in a female kid until she becomes pregnant and has her first abortion. The infection can worsen when a carrier is stressed.
To protect your animals from this infectious disease, farmers need to ensure that they are vaccinated before breeding season. They must do this before the mating period because the vaccine will not offer protection against this disease once the fetus is infected.
The vaccine administered is an oil-based, inactivated vaccine manufactured by Onderstepoort Biological Products (OBP). It is ideal for you to administer this vaccine four to six weeks to the mating season.
What can you do during an outbreak?
Vaccinating against this disease may protect your livestock. You are recommended not to administer a live vaccine during an outbreak. However, if you have had them vaccinated after being infected, the ewes would still have abortions. This is because the vaccines offer protection against the disease and not a cure to the infection.
However, infected ewes should be vaccinated to reduce the shedding of the pathogen. This helps to decrease the chances of infecting healthy one ewes.
During an outbreak, Tetracycline antibiotic injections may be given to control the disease and its spread. However, the downside of using this antibiotic shot is that it does not kill all the stages of the Chlamydophyla, and it is expensive to use.
Vaccinating against enzootic abortion
While Ovilis Enzovax is an attenuated vaccine, it is also regarded as a form of active immunization of breeding ewes susceptible to an enzootic abortion. This can offer your livestock protection against the disease if administered right.
It is adopted as a preventive measure against the infection. The best thing about this vaccine is that it offers immunity that will last for two years.
This means that farmers get to save the costs of administering it annually, and this is unlike other vaccines. Do not vaccinate animals that are already pregnant or livestock treated with antibiotics, especially tetracyclines.
- Enzootic abortion in sheep – msd-animal-health
- Abortions – Angora