A very common cause of abortion is Brucellosis, which can also infect humans. Brucellosis is an infectious disease caused by the Brucella bacteria. Brucellosis is a bacterial infection affecting primarily cattle, buffalo, pigs, sheep, goats, camels and dogs, and occasionally horses. People can catch the disease from animals. Brucellae may enter the body through mucousmembranes, conjunctivae, wounds, or intact skin in both humans and animals.
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).
Brucellosis is caused by four strains of the bacterium Brucella, in various livestock.
In cattle it is caused almost exclusively by Brucella abortus, although occasionally Brucella melitensis or Brucella suis may be implicated if cattle come in contact with small ruminants and pigs respectively
Melitensis occurs primarily in sheep and goats; suis in pigs, Brucella canis is confined to dogs
The disease in humans, sometimes called Undulant Fever, is a serious public health problem, especially when caused by Brucella Melitensis. Brucellosis in humans resembles malaria, and is often mistaken as such unless identified through laboratory testing. Cure of Brucellosis in humans requires a very long (2-3 months) and expensive treatment with antibiotics.
In animals, abortion is the most obvious manifestation. Animals abort from the 7th month onwards. Cattle of all ages and sex can be infected with B. abortus, but it is primarily a disease of sexually mature female cattle, with bulls and immature animals showing little or no clinical disease. 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.
In some countries Brucellosis has been eradicated or brought under control by a program 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.
In livestock it is not possible to treat Brucellosis. However, some cattle resist infection and a small percentage of infected cows spontaneously recover.
Mode of spread
Natural transmission occurs by ingesting the bacteria, which are present in large numbers in aborted foetuses, foetal membranes and uterine discharges. Cattle may ingest contaminated feed or water, or lick contaminated genitals of other animals.
Venereal transmission by infected bulls to susceptible cows appears to be rare. Brucella may enter the body through mucous membranes, the conjunctiva, wounds or intact skin.
The disease is spread when aborting animals discharge B. abortus bacteria in the placenta, foetus and vaginal discharges to the ground, where they can survive for several weeks. Excretion of the bacteria may occur for several days before abortion and for some time after. Cattle become infected when they ingest or inhale contaminated material. Brucellae bacteria have been recovered from fetuses and from manure that has remained in a cool environment for more over 2 months. Exposure to direct sunlight kills the organisms within a few hours.
A cow’s tail, heavily contaminated with infected uterine discharges, may spread infection if it comes in contact with the conjunctiva or intact skin of other animals. The placenta, placental fluids, and foetus from an aborting animal contain organisms which contaminate the vulva, tail and legs of the animal and the surrounding environment.
In in-calf females, the bacteria invade and cause abortion in the 7th month. The incubation period is about 6 weeks. It is only when a placenta exists i.e. in the second half of pregnancy, that the uterus is invaded and abortion occurs.
Shedding from the vagina largely disappears with the decrease in fluids following calving. Some cows that previously aborted shed Brucella from the uterus following normal calvings.
Transmission may occur by artificial insemination when Brucella-contaminated semen is deposited in the uterus
The disease can be transmitted to the unborn calf through the placenta by the infected dam. This disease can have serious negative economic consequences to stockmen in both modern intensive dairy systems and pastoral production enterprises.
Organisms are shed in the milk for a variable period of time in most previously infected cattle for life.
Housing or confining cattle increases the likelihood of transmission. Under free range conditions the disease is of lower prevalence.
Spread to human
Human becomes infected when in direct contact with cows at abortion, calving or in the post calving period.
Vets and stockhandlers are particularly at risk from the splashing of infected droplets into the eye.
Infection occurs in people drinking unpasteursied milk or milk products.
Symptoms include recurrent bouts of fever, headache, muscle and joint pains and and general weakness. Brucellosis is often confused with malaria and influenza.
Risks from Raw Milk
In non-pregnant infected animals the Brucella live inside the udder and are excreted with the milk. This presents a very serious health risk to anybody drinking raw milk. Brucellosis is a dangerous zoonosis. To protect yourself and your family 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 stillbirths or weak calves, retained placentas, and reduced milk yield. Usually general health is not affected in uncomplicated abortions.
In less acute 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 uterine infection.
After abortion, the afterbirth doesn’t come out (retained placenta). This can further develop to Metritis (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.
Calves infected before puberty usually lose the infection once removed from the source of contamination.
Mature non-pregnant animals, or animals in early pregnancy, when exposed to infection, are more likely to develop immunity than to show symptoms of disease.
Prevention of Brucellosis
Non infected herds must be protected. The greatest danger is from replacement animals. Additions should be vaccinated calves or nonpregnant heifers. If pregnant or fresh cows are added, they should originate from Brucellosis-free areas or herds and be seronegative. Replacements should be isolated for around 30 days and retested before being added to the herd.
Control – Treatment
The disease can be controlled by managing effective sanitary measures in the cattle environment. Vaccination. Calves under eight months can be vaccinated with live vaccines to prevent infection. Such vaccinations can provide lifelong immunity. However, the live vaccine should be used with care in adult animals because it can cause abortion in in-calf females and inflammation of the testes in adult males. Adult cattle should be vaccinated annually
Because of the danger of human infection, infected fetuses, placenta and cows should be handled with great care. Handlers of such material should always wear gloves for protection. They should also ensure that keep their hands away from the mouth, nose and eyes until after the hands are thoroughly disinfected.
Contact Jaguza Support