By Spy Uganda
It is estimated that around 20% of losses in livestock production worldwide can be attributed to animal diseases. In Southern Africa, tick-borne diseases remain some of the key illnesses responsible for preventable economic losses in livestock production. Global warming is also inevitably making it possible for implicated vectors to survive in geographies where they did not traditionally occur before, or at least not in numbers high enough to create a disease concern.
Anaplasmosis is a severe disease of mostly cattle, even though the infection has also been described in sheep, goats and other wild species. This disease, transmitted by infected ticks, exhibits the most prominent clinical signs in cattle and is therefore commonly assumed to be exclusive to cattle.
Anaplasmosis is often wrongly used to describe certain disease conditions like ordinary constipation (dry anaplasmosis), ingestion of certain toxic plants, or any condition which on post-mortem carcasses present with a swollen gall bladder.
The parasites found in ticks that cause the disease are Anaplasma marginale and Anaplas ma centrale. They infect ticks when they bite and feed on infected animals or previously recovered animals that have become carriers. A. marginale often leads to severe disease and deaths.
A. centrale is less harmful and used in vaccine production to help protect animals against losses associated with A. marginale.
The disease is transmitted predominantly by blue ticks, even though transmission by other tick species and mechanical transmission by blood-sucking insects has been reported. Tools and equipment that make contact with infected biological fluids (mostly blood) during veterinary procedures have also been implicated in disease transmission.
Once in the herd, the disease can be transmitted to other cattle when one needle is used to inject several animals. Other veterinary procedures such as dehorning, branding, castration, ear-notching and tattooing can also place animals at risk if the necessary hygiene precautions are not taken. The disease can also be transmitted to calves from their pregnant mothers.
The disease is much more widespread than other tickborne diseases, driven mostly by the presence and survival of host ticks. In South Africa the disease has been reported in all nine provinces, but to a lesser extent in drier parts of the country that receive very low rainfall.
How Can Disease Be Recognized
In some cases, the disease may remain undiagnosed but may manifest through fever (high body temperature), progressive anaemia and icterus (seen through yellowish discolouration of mucous membranes of, for example, the eyes, gums and vulvae). All ages of cattle are susceptible to infection but the severity of the disease seems to increase with age, especially after two years of age, while calves under six months may generally be temporarily resistant to the disease.
In the acute phase of the disease, owners may notice a rapid decline in milk production, rapid breathing, excessive salivation, nervous signs, loss of appetite, weight loss, abortions and lethargy. Infected animals are known to exhibit signs of constipation, often witnessed as very dry, bile-stained (and even bloody) dung. Severely affected animals may likely die if not treated correctly on time.