A study on bovine theileriosis

Bovine theileriosis is a tick borne protozoan infection that affects many animal species around the globe. It has a significant adverse effect not only on the productivity of animals but also sometimes it proves to be fatal if left untreated. Mortality caused by T. annulata varies from 5 percent or less (in indigenous breeds) to 90 percent (in introduced exotic breeds). Nearly 80 percent mortality has been reported in young calves as compared to adult ones that shows less than 10 percent mortality.
Etiology:
Bovine theileriosis is caused by intracellular protozoan that mainly consist of five different species. The two most important among them are; Theileria annulata (T. annulata), widespread in almost all parts of the world like Southern Europe, North Africa and Asia while Theileria parva, is prevalent in East and Central Africa. T. parva and T. annulata lead to lympho-prolipherative disease with high mortality and morbidity in cattle generally known as East Coast fever and tropical theileriosis, respectively. Throughout the world, tropical theileriosis is an economically significant disease of cattle. T. annulata causes a severe and often fatal disease in bovine in tropical and sub-tropical region. Importantly it causes acute and fatal infection in susceptible newborn calves and lead to death within 5-15 days after the onset of clinical disease.
Theileriosis results from infection with protozoa in the genus Theileria is an obligate intracellular parasites. The two most important species in cattle and buffalo are T. parva, which causes East Coast fever, and T. annulata, which causes tropical theileriosis.
Transmission:
Theileria spp. is transmitted by ticks acting as biological vectors. Rhipicephalus appendiculatus is the most important vector for T. parva while T. annulata is transmitted by ticks in the genus Hyalomma. Hyalomma spp.
Clinical signs:
The parasite causes lymph proliferation in its early phase (schizonts phase) manifested as enlargement of lymph nodes, which subsequently leads to lymph-destructive phase identified by marked leucopenia. In the parasitaemia phase, the parasite becomes infective for the tick. General weakness, anorexia, high rectal temperature, weight loss, anemia, in conjunctiva mucosa petechial hemorrhages become prominent, swelling of enlarged lymph nodes and cough is the main clinical symptoms. The clinical reactions in the infected animals were pyrexia (40.5–41.5 8C), enlargement of superficial lymph nodes, nasal and ocular discharges, salivation, anemia, and respiratory distress. Although anemia mechanism is still not clear in theileria infected calves. Even then anemia is considered as major characteristic of T. annulata infection in animals.
Diagnosis:
Diagnosis of theileriosis is mainly dependent on clinical signs as well as on microscopic examination of Giemsa-stained lymph nodes and blood smears. Developments of sensitive and specific diagnostic assays have become possible only with the advent of the polymerase chain reaction (PCR) for the detection of various pathogenic agents, including numerous theileria species, in animals.
Treatment:
Buparvaquone, anti-protozoa drug may be used in the treatment of recently infected animals with T. annulata in a single dose of 2.5 mg/kg body weight intramuscular with efficacy varied from 88.7% to 100%. Alternatively, a single dose of 5 mg/ kg is more effective. Calotropis procera (Picture 1) commonly known as ‘Ak’ or ‘Arka’ all throughout the tropics of Asia and Africa is a wild plant with multifactor characteristics can also be used for the treatment of bovine theleriosis. Peganum harmala (Picture 2) is an herbal; commonly habitant to arid and semiarid area of central Asian deserts (Rehman et al. 2009). P. harmala L. is commonly known as harmala. The plant had multipurpose medicinal activities and could be used in chemotherapeutic purpose against the bovine theileriois.
Control:
Theileriosis is not transmitted by casual contact. If the infection is newly introduced to an area, it might be eradicated with movement controls, by culling infected animals and by preventing ticks from becoming infected. In endemic areas, the tick burden can be decreased with acaricides and other methods of tick control such as rotational grazing. The transfer of blood between animals must also be avoided. Antiparasitic drugs are effective in animals with clinical signs, but animals may remain carriers. Treatment is most effective in the early stages of the disease. Animals can be protected from both East Coast fever and tropical theileriosis by vaccination. Attenuated vaccines are used to control tropical theileriosis in some countries.
DR MUKHTAR AHMAD
Department of Clinical Medicine and Surgery, UVAS, Lahore