THE issues of global changes, climate change and tick-borne diseases cannot be ignored, given they are now becoming the order of the day.
Cattle and other livestock, the world over, are experiencing both ecological and biological stress which could affect the wellbeing of livestock globally and ultimately the well-being of man.
Every year, many cattle herds in Africa are depleted from vector-borne diseases, such as Theileriosis, according to the World Health Organisation (WHO).
At a conference held in Spain, in 2015, on the Impact of Environmental Changes on Infectious Diseases (IECID), a keynote speech was given on climate change, biodiversity, ticks and tick-borne diseases which revealed the inter-dependency of climate and the ecology and how they impact tick-borne diseases.
Since 2015 in Zimbabwe, livestock farmers have battled with encounters of Theileriosis, commonly known as January disease because of its prevalence during that month.
Though Zimbabwe had partly recovered from the effects of Theileriosis on the national herd in the 2017/2018 farming season, many rural cattle producers, especially in Mashonaland West, Mashonaland Central and Mashonaland North, have reported a resurgence of the disease this farming (2023-2024) season.
Due to climate change, the late rains, with intervals of extreme heat and high humidity that Zimbabwe is currently experiencing, are particularly conducive conditions for the reproduction of ticks and midges that afflict cattle and other small livestock. For eight years, since 2015, many herds have been decimated throughout Mashonaland West and Central by disease as well as fire, as many communal kraals have been gutted by fire as farmers attempt to prevent further spread of the diseases.
World concerns about climate change and its effects on ticks, particularly on livestock, need to be heeded.
The scientific evidence for rapid climate change is compelling and alarming. Most experts in the field have now reached a consensus that ‘the earth’s climate is indeed changing’. Zimbabwe needs to be forewarned and in a state of preparedness for these far-reaching changes and consequences.
According to experts, climate change is modifying the environment where we live and our way of living. The burden of vector-borne and climate-sensitive diseases is greatest for the poorest populations, especially in Africa. For example, the per capita mortality rate from vector-borne diseases is almost 300 times greater in developing nations than in developed regions.
In addition, vector-borne disease risks are typically much greater for poor individuals within any population owing to poorer environmental and social conditions (like lower-quality housing situated closer to vector-breeding sites), and lack of access to preventive and curative health interventions and services, particularly the rural communities and farmers.
The effect of climate change — particularly of increasing temperatures — in tropical zones may be deleterious to some species, adversely affecting habitat suitability and forcing certain tick species to colonise new areas.
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 shows that ticks have already expanded into previously inhospitable areas as a result of higher temperatures due to global warming. This means that Zimbabwe’s Eastern Highlands would now be suitable for cattle farming, and that would likely see the arrival of ticks.
In Southern Africa, for example, it has been predicted that increasing the temperature by 2° C will decrease habitat suitability for four tick species — the African blue tick (rhipicephalus decoloratus), the South African bont tick (amblyommahebraeum), the brown ear tick (rhipicephalus appendiculatus) and the small smooth bont-legged tick (hyalommatruncatum).
Another study suggests that the progressive increase in temperatures seems to be forcing the dispersion of tropical bont tick (amblyommavariegatum) towards areas outside of zones that have prolonged dry spells, such as Zimbabwe experienced in the recent past.
The study of tick activity, reproduction and survival depends on several factors which, in turn, have a direct impact on tick distribution and abundance. These include vegetation coverage, host availability, moisture and temperature conditions (which are currently at peak suitability in Zimbabwe) and human activities.
While there has been a marked increase in research output on climate change and health in recent years, with vector-borne disease among the better-represented subject areas, a complete understanding of all aspects involved in the transmission dynamics of tick-borne pathogens is possibly beyond current human capabilities. Additional knowledge on ticks, animals, pathogens and their interactions with the entire ecosystem is essential.
Climate is an important influence on vector-borne disease transmission, such as Theileriosis/January disease, and there is evidence that ongoing climate change is affecting, and will continue to affect, the distributions and burdens of these infections. Theileria parva is changing from seasonal to non-seasonal, with rapid spread and high mortality. Due to the high costs of Theilericidal drugs and the high costs of treatment of Theilerial infection, prevention is the best means to control the vector ticks. Manual removal of ticks is a common practice, but must be done correctly
The resurgence of Theileriosis, or January disease, a serious disease of cattle in Zimbabwe in 2024, is both, alarming and disheartening. Theileriosis is a specified disease in Zimbabwe and should be reported timeously and tackled effectively. Increased awareness, education and inclusion of small-scale farmers would increase the success of livestock diseases surveillance and control operations in Zimbabwe if carried out professionally and judiciously.
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
