Theileriosis disease: economic threat to livestock industry and its control strategies
Theileriosis is tick born protozoan parasitic disease in livestock population. It is due to Theileria parva (East cost fever) and Theileria annulata (Tropical or Mediterranean). Tick born diseases causes huge economical losses in dairy industry in tropical and subtropical areas where 80 percent of world total cattle population live.
Tick transmitted Theileriosis commonly known as East-Cost fever that probably the most important livestock disease in Africa. It cause annual loss of 1.1 million cattle and $ 168 million as of 1992. Sudan, South Africa, Swaziland, Zimbabwe, Zambia, Tanzania, Kenya, Uganda are home of this disease.
In Pakistan environmental conditions favor the ticks. That is why tick can transmit the diseases to humans, livestock as well companion animals. In Indo-Pak the T.annulata is more common in all species. This include cattle, buffalo, and up to some extent in small ruminants.
There are 6 species of Theileria but the most pathogenic and economically important are Theileria parva and Theileria annulata.
Most often disease occur in sub-clinical form leading significant economic losses. Without treatment the fatality reach up to 80 percent in exotic breeds (Boss Taurus) as compared to ingenious breed (Bos indicus) with 20 percent.
T.annulata cause severe losses in dairy industry in endemic countries including Africa and Asia. The primary vectors for Theleria are Ticks (Ixodidae family). The T.parva was first reported in Zimbabwe in 1902. However misdiagnosed as Redwater (a disease caused by protozoa Babesia bigemina).
High temperature as well humidity is supportive for tick growth. A form of east cost fever is corridor disease, appear when organism transmit from the African buffalo to cattle.
Theileria species are the only eukaryotic organism known to transform the Lymphocytes. Life cycle of these organism is completed in the Lymphocytes (Schizonts) and in RBCs (Piroplasm).
Theileriosis0 utilize WBCs and RBCs for life cycle completion in mammals. The highly pathogenic species of Theileria (T.parva and T.annulata) parasitic multiplication occur within the WBCs of host. Less pathogenic species occur in the RBCs.
Clinical signs include swelling of pre-scapular lymph nodes, temperature 106 F after 7-10 of infecting ticks. Bulged eyes, anorexia, emaciation, nasal discharge, dyspnea, lacrimation, corneal opacity, sometime shizonts and piroplasm block the capillaries. It leads to hypoxic injury in brain (nervous signs), poor growth, anemic, jaundice due to destruction in RBCs.
Just before death a sharp decline in body temperature and pulmonary exudates oozes out from nostrils. Autopsy signs involving myocardial degeneration, pulmonary edema, lymph nodes enlargement.
Hemorrhages in liver, spleen and milk clots in Abomasums is typical for theileriosis in calves. Theileriosis differently diagnosed from Trypanosomiasis (largest blood parasite extracellular), Babesiosis (Haemoglobinurea).
Control can achieve by development of disease resistant ticks. Domestic animals free from ticks are the major concern in tropical countries with large livestock populations especially in Indo-Pak region.
Control of high temperature and humidity is essential to control theileriosis disease. Because it is favorable for tick survival. Chemicals pesticides (acaricides) need to apply in dipping baths, spray races. As well as, use of cattle breed with good ability to acquire immune resistant to the vector ticks. Sahiwal breeds in Indo-Pak region are best solution for control measures.
Hence, we can avoid from haemoprotozoan diseases by proper control strategies. In this regard by applying such control measures we can minimize our economic losses in terms of health as well production of animals of domestic importance.
This article is collectively authored by Dr. Rashid Fayyaz , Dr. Asghar Abbas, Dr. Rao Zahid Abbas, Dr. Safdar Imran and Dr. Tahir Aleem.