BY DR TONY M. MONDA
Documents show that while agriculture contributes 11% to gross domestic product and livestock’s own 22% contribution to the agricultural GDP are recognised; the full contribution of livestock at every level is not always fully appreciated.
The significant role that livestock plays in human nutrition, foreign currency earnings, employment creation and across the value chain, are not always taken into full account.
There is potential to use livestock and the livestock industry as an engine to drive further economic growth by implementing regulations and activities to monitor and control to eradicate diseases which are impacting negatively on the livestock sector and on farmers already challenged by the vagaries of climate change.
Climate change is having substantial effects on ecosystems and the natural resources upon which the livestock sector depends. Climate change affects the sector directly, through increased temperature, changes in the amount of rainfall and shifts in precipitation patterns. Indirect impacts will be experienced through modifications in ecosystems, changes in the yields, quality and type of feed crops, possible increases in animal diseases and increased competition for resources.
According to The Cattle Site News Desk, a research published in SciTechnol, an online scientific journal, established that global warming might allow some tick species to thrive in areas in which they previously could not survive. Evidence from other countries show that ticks have already expand into previously inhospitable areas as a result of higher temperature due to global warming.
This means that in Zimbabwe, Zimbabwe’s Eastern Highlands would now be suitable for cattle farming, and that would likelywitness the appearance of ticks in the area.
Ticks and tick-borne diseases have major impacts on livestock productions. Theileriosis is a serious disease of cattle caused by a species of Theileria – a blood-borne parasite. It only affects cattle and is primarily transmitted by ticks. Theileria is a widespread disease in Zimbabwe, with an increasing number of cattle deaths reported annually, especially among rural farmer, since 2015, when tick- borne diseases killed 3,430 cattle between November and May — nearly twice as many as died during the same period in 2013/14.
Theileria are microscopic protozoa. Other examples include: malaria in people, coccidiosis in animals and birds, especially poultry and tick fever in cattle.
To become infected by Theileria, cattle must be bitten by a tick carrying the disease. It is not spread by direct animal to animal contact. Cattle can be infected with the Theileria parasite without necessarily showing any signs of clinical disease.
Theileriosis only affects cattle and is transmitted by cattle ticks;
Theileriosis causes anaemia in cattle and can be fatal;
Cows during calving and young calves (2-3 months) are at most risk from infection.
Once the animal is bitten, it takes about 6-8 weeks for the parasite to build up the significant levels
in the blood.
Theileriosis is also known by several other names – eg: East Coast Fever, Corridor Disease,
Theileriasis, January Disease, Zimbabwean Tick Fever, African Coast Fever; Tropical Theileriosis,
Mediterranean Coast Fever and Mediterranean Theileriosis History and timeline of Theileria parva in Zimbabwe
•1901/2 East Coast fever introduced;
•1934 Corridor disease recognized;
•1936 Zimbabwe theileriosis (January disease) recognized;
•1954 East Coast fever eradicated, Corridor disease and Zimbabwe theileriosis persist
The Brown Ear Tick Rhipicephalus appendiculatus is the main vector of Theileria parva
•Three host tick;
•Preferred hosts are cattle and large wild ungulates;
•Adults feed preferentially on the ears;
•Immatures feed on the head and neck;
As climate change brings more extreme and uncertain weather, as well as warmer conditions in
many places, concerns about such pest outbreaks are growing. Theileria parva is changing from
seasonal to non-seasonal, with rapid spread and high mortality
Etiology Theileriosis results from infection with protozoa in the genus Theileria of the suborder
Piroplasmorina. Theileria spp. are obligate intracellular parasites. The two most important species in cattle and water buffalo are T. parva, which causes East Coast fever, and T. annulata, which causes tropical theileriosis.
A number of other Theileria species including T mutans, T buffeli, T. velifera, T. taurotragi and T.
sergenti can also infect domesticated and wild ruminants. Many of these organisms are carried
asymptomatically, but some can cause anaemia, and concurrent infections may increase the severity of East Coast fever or tropical theileriosis.
T lestoquardi (formerly T. hirci) is the most virulent species in sheep and goats. T. separata and the non-pathogenic species T. ovis also occur in small ruminants.
Species Affected
T. parva can infect cattle, African buffalo (Syncerus caffer), water buffalo (Bubalus bubalis), and
waterbucks (Kobus spp.). Symptomatic infections are common only in cattle and water buffalo. T. annulata occurs in cattle, yaks, water buffalo and camels. Mildly pathogenic and non-pathogenic species found in cattle include T. mutans, T. buffeli, T. velifera, T. taurotragi and T. sergenti.
T. taurotragi has also been recognized in eland. Theileria spp. have been found in most wild Bovidae in
Africa. They have also been reported in wild animals on other continents.
T. lestoquardi, T. separata, T. ovis and other species occur in sheep and goats.
Geographic Distribution
T. parva (East Coast fever) is found in sub-Saharan Africa, including in Zimbabwe. T. annulata
(tropical theileriosis) occurs from southern Europe and the Mediterranean coast through the Middle East and North Africa, and into parts of Asia.
T. parva and T. annulata are not usually found in the same region; these two parasites seem to occur together only in southern Sudan.
T. mutans has been found in African and on some Caribbean islands, and was reported from the US in 1950 and 1975. T. velifera and T. taurotragi occur in Africa, while T. sergenti has been reported from parts of Asia. T. buffeli is widespread, and has been reported from Europe, Asia, Australia, North America and parts of Africa.
T. lestoquardi has been documented in Asia, the Middle East and parts of Africa and Europe. T. ovis and T. separata occur in Asia.
Dr.Tony M. Monda BSc, DVM, DPVM, is conducting Veterinary epidemiology, disease control, agro-climatology and agro-economic research in Zimbabwe. E-mail: tonym.MONDA@gmail.com
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