Tick-borne diseases spreads from wild animals to humans: what we need to know

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Grant No  : RG/2019/BT/01 

Project title
Tick-borne spotted fever group rickettsioses in the Central Province: types of pathogens, vertebrate reservoir host community composition and tick species involved in circulation and maintenance of pathogens
Principal Investigator
Prof. Rupika Rajakaruna, Dept. of Zoology, Faculty of Science, University of Peradeniya 

Many tick-borne diseases (TBDs) are emerging globally, causing severe illness and death in humans and domestic animals. Although humans are incidental hosts of ticks, there are rising infection rates of TBDs due to increasing contact with wildlife, especially when domestic animals encounter wild animals in overlapping habitats. Among TBDs, spotted fever group rickettsial (SFGR) infections have a high prevalence in the central hills of Sri Lanka. TBDs are transmitted to humans when they are bitten by ticks carrying the pathogens. The symptoms of tick-borne rickettsial fever typically include fever, headache, muscle aches, and a spotted rash. The severity of the illness can vary, and in some cases, it may lead to more severe complications if not treated promptly with appropriate antibiotics.

While numerous cases of spotted fever have been reported in the central hills of Sri Lanka, there is limited information available regarding the bacterial species causing the disease, the tick species transmitting the disease, and the animal reservoirs. Researches collected blood samples and ticks from domestic and wild animals, and skin biopsies from rickettsia diagnosed patients at the hospital. It was found that tick species that infest dogs, cattle, mongooses, and squirrels play a significant role as competent reservoir hosts as they frequently harbor the common tick species carrying DNA of rickettsial bacteria. This indicates that these vertebrates play a role as reservoir hosts for TBDs. Also it was found that TBDs such as Babesia, Anaplasma, Hepatozoon, and Ehrlichia in domestic animals were common, especially in dogs and pigs. Among dogs, free-roaming mongrels were asymptomatic and carried parasites at low levels which was not detected in usual blood smear tests.

A community survey carried out by the researchers showed various household and natural products including some plant extracts used to control ticks as local remedies in addition to commercial acaricides. Community knowledge on TBDs and especially human rickettsial infections was poor although they sought professional advice by visiting healthcare facilities. Increased awareness about the importance of avoiding tick bites as they tend to carry TBDs in both humans and domestic animals is important.

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