Cattle ticks of the genera Rhipicephalus and Amblyomma of economic importance in Tanzania: distribution assessed with GIS based on an extensive field survey

Abstract

In order to implement a robust integrated tick and tick-borne disease control programme in Tanzania, based on ecological and epidemiological knowledge of ticks and their associated diseases, a national tick and sero-surveillance study was carried out in all 21 regions of the mainland, as well as on Mafia Island, between 1998 and 2001. The current distributions of Rhipicephalus appendiculatus, R. pravus, Amblyomma variegatum, A. gemma, and A. lepidum are illustrated and discussed. Tick distribution maps were assessed using the Weights-of-Evidence method (WofE), and employing temperature, humidity, NDVI, rainfall, and land-cover predictive data. Ground-truthing was done to check correspondence both of the data employed in prediction with land-cover characteristics discerned in the field as well as of the surveyed and predicted tick distributions. Statistical methods were used to analyse associations of the tick species with their environment, cattle density, and other ticks. Except for R. appendiculatus, no appreciable changes were demonstrated in the predicted and observed tick distributions compared to the existing maps that originated in the 1950-1960s. Cattle density influenced the distribution of A. variegatum and, to a certain extent, of A. lepidum, but had no appreciable influence on the distribution of any of the other ticks discussed in this paper, neither did livestock movement. Distinct differences for environmental requirements where observed between different tick species within the same genus. The predictive maps of R. appendiculatus and R. pravus suggest their mutually exclusive distribution in Tanzania, and simultaneous statistical analysis showed R. pravus as a greater specialist. Of the three Amblyomma species, A. variegatum is the most catholic tick species in Tanzania, while both A. gemma and A. lepidum belong to the more specialized species. Despite dissimilar habitat preferences, all three Amblyomma spp. co-exist in central Tanzania, where very heterogeneous habitats may simultaneously satisfy the environmental requirements of all three species. The current study, conducted about 4 decades after the last major survey activities, has shown that changing livestock policies, unrestricted livestock movement and a continuous change in climatic/environmental conditions in Tanzania have brought about only limited changes in the distribution patterns of R. appendiculatus, R. pravus and the three Amblyomma species investigated. Whether this observation indicates a relative indifference of these ticks to environmental and/or climate changes allows room for speculation.

Abundance and distribution of Ixodid tick species infesting cattle reared under traditional farming systems in Tanzania

“…It was also observed across all the three regions. This species is the most common and widely distributed in Tanzania, covering sub-humid and low-to-high altitudes of the country (Lynen et al, 2007). The observations in our study are similar with the observations from a study by Swai et al (2005) on tick management systems in Ngorongoro district of Tanzania.…”

“…In Tanzania, Ixodid ticks of the genera Rhipicephalus and Amblyomma are the most important and widely distributed species found in many parts of the country where cattle are raised (Yeoman and Walker, 1967;Lynen et al, 2007;Kwak et al, 2014;Laisser et al, 2014).…”

Serological survey of antibodies to Ehrlichia ruminantium in small ruminants in Tanzania

“…tick vectors but associations between lowland habitats and Amblyomma spp. are not general amongst studies (Lynen et al 2007) and in the present study animals in the semi arid Kilindi and Handeni districts were also more likely to have seroconverted to E. ruminantium despite the association being not significant. Nevertheless, some animals, particularly sheep, in all AEZ's and grazing management systems seroconverted to E. ruminantium, indicating a widespread distribution of tick vector species in the study districts.…”

Genetic characterization of ticks from southwestern Romania by sequences of mitochondrial cox1 and nad5 genes

“…Previous studies on ticks have been focused mainly on their morphology, distribution, epidemiology, diagnosis, treatment and prevention, as well as transmission of diseases (e.g., Willadsen 2006;Lynen et al 2007;Yin and Luo 2007;Dantas-Torres 2008). However, only limited work has been done in the molecular characterization and phylogenetic studies of ticks (Black and Piesman 1994;Caporale et al 1995;Black et al 1997;Black and Roehrdanz 1998;Geraci et al 2007).…”