Three of the most hazardous and costly venereal diseases among livestock in South Africa are brucellosis, trichomoniasis and pizzle rot. Dr Andy Hentzen, a veterinarian and lecturer at the University of Pretoria who has both national and international experience in production medicine and management, sat down with Stockfarm to discuss how best to manage and prevent these diseases in cattle and sheep.
Prevalence of brucellosis
Brucellosis is a highly contagious disease caused by the bacterium Brucella abortus. Symptoms include abortion, lowered fertility rates and decreased milk production. Full-term, weak calves that die shortly after birth is also a common occurrence in infected herds. Serological tests, such as the Rose Bengal test or milk-ring test, are excellent diagnostic tools that can help to identify an outbreak in a herd.
According to Dr Hentzen, brucellosis is quite common in cattle, but infections also occur in sheep. “Widespread outbreaks of brucellosis occur in all provinces in South Africa. The number of incidences per year is not known, but most people agree that the annual number of bovine brucellosis cases is climbing.”
This disease can also be transmitted to people through cuts in the skin, mucous membranes, or by eating contaminated meat or other animal products. Dr Hentzen adds that brucellosis is a state controlled and notifiable animal disease in terms of the Animal Diseases Act, 1984 (Act 35 of 1984), which means that infected animals must be reported to a state veterinarian.
Trichomoniasis in cattle
Trichomoniasis is a highly contagious venereal disease in cattle. It is caused by the rather small, motile protozoa organism Tritrichomonas foetus and is only found in the reproductive tract of infected cows and bulls.
“Like brucellosis, the specific number of local incidences of bovine trichomoniasis is not known. It has been noted that the incidence rate of this disease has been increasing over time. For that reason, the disease is now more commonly found in South Africa compared to a few years ago,” says Dr Hentzen.
There are often no visible symptoms. The first indication of the disease’s presence is a lower than normal conception rate, usually diagnosed during a regular pregnancy diagnosis. This means it can only be confirmed through diagnostic testing. The disease can cause early foetal death, pyometra (puss in the womb) and infertility, resulting in extended calving intervals.
Occurrence of pizzle rot in sheep
Pizzle rot (Enzootic balanoposthitis), also known as peestersiekte, is caused by Corynebacterium renale and Mycoplasma mycoides, among other bacteria, and occurs predominantly in sheep, although infections have also been reported in Angora goats. The disease can be found throughout South Africa.
Pizzle rot causes ulceration and irritation of the skin surrounding the preputial opening, giving bacteria such as C. renale an opportunity for further infection. Symptoms in rams include inflammation of the penis and sheath. This painful condition can cause severe interference with urination and makes it difficult or even impossible to use affected animals for breeding. Ewes can contract the disease during mating, which is why affected rams and ewes must be separated from the flock and treated immediately.
Control and eradication of venereal diseases
Blood tests are normally used to detect the presence of brucellosis in cattle; the same method is used to confirm brucellosis in rams and positive cases are usually culled.
According to Dr Hentzen, private veterinarians will report positive cases to the state veterinarian and will also keep them up to date as to any follow-up information pertaining to the outbreak. “With the help of private or state veterinarians, livestock producers will be able to control and possibly eradicate the disease in their herds. If a livestock producer suspects an animal might have brucellosis, it is vital to isolate that animal from other healthy animals immediately to prevent the disease from spreading,” he adds.
If trichomoniasis is suspected in a herd, the bulls must be tested by collecting a sample via sheath washing, which is then sent to a laboratory. Dr Hentzen explains that trichomoniasis-positive bulls need to be culled, since most bulls remain carriers. However, if the animal has significant value, a veterinarian can be consulted for alternative treatment options.
“It should be noted that these alternative treatments are not always successful. It is generally accepted that the likelihood of transmission via cows will decrease after three normal heat cycles. A vaccine can be administered to control and decrease the incidence of trichomoniasis. Livestock producers can also resort to artificial insemination, which is one of the most effective ways of eliminating the spread of the disease.
“If you want to prevent an outbreak of trichomoniasis in your herd, it is best to utilise bulls that have tested negative for the disease before the mating season commences, or to use bulls that have never mated before for breeding. It is also important to consult your veterinarian about herd-specific measures that are applicable to your unique farming environment,” says Dr Hentzen.
When it comes to pizzle rot, both rams and ewes must be regularly inspected for signs of the disease. Handlers should wash and disinfect their hands after handling each animal, so as to prevent the disease from spreading from one animal to another. Infection should ideally be identified early in order to minimise any chronic damage that could hinder future breeding in both male and female animals.
Prevention and treatment of venereal diseases
The focus should always be on preventative rather than curative measures. This rings true for all livestock diseases, but is especially important when it comes to venereal diseases that can significantly affect a producer’s profitability. Brucellosis is no exception. “There is no treatment available for infected animals, which means they need to be culled. In this sense, the best way to fight brucellosis would be to prevent infection through vaccination,” explains Dr Hentzen.
Reproduction is one of the biggest profit drivers in livestock farming. The cost of lower reproduction far exceeds the costs of medicine, vaccines and diagnostic tests.
Similar to the prognosis of brucellosis, there is no treatment available for bovine trichomoniasis. Identifying bulls with trichomoniasis prior to the breeding season is therefore crucial. The diagnostic test for bulls involves the microscopic examination of cultured preputial samples and/or a laboratory test where the organism’s DNA (polymerase chain reaction, or PCR) is tested.
Pizzle rot can be treated very successfully with antibiotics. Once the affected rams have been isolated, aerosol antibiotics can be sprayed onto the affected area and a long-acting antibiotic can also be administered. Rams should not be used for breeding purposes until all the ulcers have completely healed. Pizzle rot has no direct effect on ewes’ fertility and they usually recover by themselves within a few weeks.
In terms of prevention, producers should consider adjusting the protein level of sheep’s diet to below 16%. Tick control should also be reinforced throughout the year, as ticks can aid in the transmission of the disease.
In conclusion
According to Dr Hentzen, the stated diseases all affect reproduction in one way or another. The result is often a lower than normal lamb and calf crop, which affects herd or flock growth and creates economic uncertainty for the producer.
“Reproduction is one of the biggest profit drivers in livestock farming. The cost of lower reproduction far exceeds the costs of medicine, vaccines and diagnostic tests. It is therefore prudent to prevent these diseases by all means necessary,” he concludes. – Claudi Nortjé, Stockfarm
For enquiries, contact Dr Andy Hentzen
on 082 372 0307 or andreas.hentzen@up.ac.za.
