Our disease investigation unit at the Western College of Veterinary Medicine at the University of Saskatchewan is helping a veterinarian investigate a serious outbreak of abortions in a goat herd. These investigations are funded by the Saskatchewan agriculture ministry and are always carried out in co-ordination with the local veterinarian.
Abortion outbreaks are often devastating and are usually difficult to deal with because by the time the abortions are identified, the infections have spread throughout the herd or flock.
The suspected cause of the abortions in this case is a disease known as Q-fever. The unusual name of Q-fever came about when the disease was first discovered in sheep in Australia and a definitive cause could not be established and so the Q stood for “Query.”
Q-fever is a zoonotic disease (it can be spread from animals to humans) found worldwide and is caused by a bacterium known as Coxiella burnetti. Cattle, sheep and goats are the primary reservoirs of the bacteria, although other species such as domestic cats can also be a source.
The organism can also spread among wildlife populations via ticks and other insects.
Most animals do not show significant clinical signs when infected, with the exception of goats and sheep.
Cattle may show evidence of reduced fertility, but the primary sign of infection in small ruminants (sheep and goats) is abortions.
In some cases, abortion storms have occurred, where a large proportion of the flock have aborted due to infections with the Q-fever organism.
The organism that causes Q-fever tends to reside in the udder and placenta of infected animals, and is excreted in large numbers in milk, placental tissue, fetal fluids, urine and feces.
It is quite resistant to heat, drying and disinfectants and can survive for weeks or even months in the environment.
The greatest risk of transmission to other animals and to people occurs at lambing or kidding time. The organism can be inhaled, ingested or spread by direct contact with birth fluids and placenta.
Drinking unpasteurized milk from infected ruminants can also be a source of the disease.
Q-fever has a highly variable presentation in humans and most commonly shows up as a mild flu-like illness. However, a smaller proportion of cases can be affected with a severe pneumonia, hepatitis or endocarditis.
Human Q-fever is primarily an occupational disease of farmers, veterinarians and laboratory workers who work with sheep, or abattoir workers.
Pregnant women and immunocompromised people need to be especially careful about avoiding infections with this organism.
Several large-scale outbreaks in people have occurred around the world. In 2007-10 in the Netherlands, more than 3,500 cases of human Q-fever were reported.
This represented a dramatic increase. Most cases were clustered around a village near several large milking goat and milking sheep operations. The small ruminant operations began to experience abortion storms due to Q-fever in 2005 and 2006.
In subsequent years, the number of human cases rose sharply and it appears that dry weather, wind-borne spread of the infection and proximity to high populations of susceptible people may have contributed to the outbreak.
There are no commercial vaccines for Q-fever available for small ruminants in North America, although human and animal vaccines have been used in other parts of the world.
Antibiotics, such as long-acting tetracyclines, can control the infection in sheep and goats during abortion storms. However, in many cases, by the time the abortion storm has begun, many animals have already become infected so it may be difficult to control the spread.
There are many other causes of abortion in sheep and goats. Q-fever is not the most common.
However, a recent case of Q-fever abortion was diagnosed at a Saskatchewan diagnostic laboratory in a goat and there is ample evidence that a significant proportion of cattle, sheep and goats in North America have been exposed to the organism.
Many of the other causes of abortion in sheep and goats are also zoonotic. Diseases such as chlamydial abortion, campylobacter, leptospirosis, toxoplasma and salmonella can all cause infections in people and are common causes of abortion in sheep and goats.
Aborting animals should be isolated for three weeks and placental tissue and contaminated bedding should be removed and destroyed by burning or composting. The lambing or kidding pen should be thoroughly cleaned and disinfected using a 1:100 Lysol solution.
The best way to prevent human infections is to wear protective clothing when assisting ewes or does with lambing or abortions. Disposable gloves should be worn and pregnant women or immunocompromised individuals should not assist in the birthing process of small ruminants.
John Campbell is a professor in the department of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.