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Eco-Epidemiology of ticks and pathogens transmitted by ticks to wild and domestic animals in South Africa (Free State and North West Provinces)

Applicant Gern Lise
Number 125492
Funding scheme Project funding
Research institution Laboratoire d'Eco-épidémiologie Institut de Biologie Université de Neuchâtel
Institution of higher education University of Neuchatel - NE
Main discipline Veterinary Medicine
Start/End 01.10.2009 - 30.09.2012
Approved amount 266'082.00
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Keywords (11)

ticks; wildlife; babesia; theileria; ehrlichia; ecology; epidemiology; lifestock; evolution; genetic; population

Lay Summary (English)

Lead
Lay summary
Ticks represent a challenge to the South African livestock industry and to game ranging and conservation initiatives mainly due to tick-borne pathogens. In South Africa, where animals and their products correspond to 48% of the agriculture production, tick-borne diseases represent considerable economic losses. The problem related to ticks is also a challenge for game ranging on game farms since this sector also became important with the increase of ecotourism. In South Africa, many farmers breed wild animals with cattle and small ruminants in order to increase their income through game viewing and hunting. In addition, game translocations, which are increasing through international conservation efforts, constitute a high risk of spreading ticks and their pathogens. Wild animals may be the origin of livestock infections by tick-borne pathogens and vice-versa. However, the role and importance of wild and domestic animals in the circulation of these pathogens are fairly unknown. Here, we intend to investigate wild and domestic animals for ticks and tick-borne pathogens. One of our aims is to clarify the situation in wildlife and domestic animals by studying the host and vector ranges of these pathogens as well as their geographic distribution. This information is essential to optimize cattle and wildlife management strategies. The second aim targets two tick and Babesia species that are currently competing in the studied area. We will compare the population genetic features of an invasive tick, Rhipicephalus microplus, and an out-competed tick, R. decoloratus and precise the outputs of their competition relative to the Babesia threats. R. microplus was introduced to Africa from Asia and is the unique vector of the very virulent Babesia bovis as well as a potential vector of the less virulent B. bigemina. Along its invasion, R. microplus is displacing the native tick R. decoloratus, a vector of B. bigemina but not of B. bovis. Combining a survey of these two Babesia among wild and domestic ruminants, and in ticks, is a prerequisite to forecast the emergence of B. bovis, and to apply protection measures. We will collect ticks and tissue samples from wild and domestic animals where they have contacts with each other and analyse them using molecular tools. To monitor the displacement of R. microplus and of B. bovis into new areas, we will investigate the borders between areas where R. microplus is known to occur and areas where this tick species has not yet been described. The population genetic analyses of both tick species will be performed.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

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Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Seven International Conference on Ticks and Tick-Borne Pathogens TTP7 29.08.2011 Zaragoza, Spain


Abstract

Ticks represent a considerable challenge to the South African livestock industry, especially the production of cattle and small ruminants, as well as to game ranging and game conservation initiatives. The main problem associated with ticks is due to their ability to transmit a wide spectrum of pathogenic microorganisms. In South Africa, animals and animal products correspond to 48% of the agriculture production, the threat to animal health caused by tick-borne diseases represent considerable economic losses. On the other hand, game ranging on game farms has become an important economic sector; ecotourism also increased over the past decades. The problem generated by tick-borne diseases is also a challenge for these sectors. In South Africa, livestock animals and game animals are frequently in contact. Cattle farms often surround the game reserve, many farmers are breeding wild animals on their farms simultaneously with cattle and small ruminants in order to increase their income through game viewing and hunting. Wild animals may play an important role in the epidemiology of tick-borne diseases; they act as maintenance hosts and reservoirs and support large tick populations. Game animals may represent the origin of livestock infections due to tick-borne pathogens and vice-versa. However, the exact role and importance of both wild and domestic animals in the eco-epidemiology of these diseases, as well as the relation between them regarding these diseases, are still fairly unknown. In addition, game translocations, which are increasingly performed through international conservation efforts and game ranging, from one game reserve to another one as well as to game farms, constitute a considerable risk of spreading ticks and tick-borne pathogens. Therefore it is of great importance to increase our knowledge concerning tick-borne pathogens in relation with their host and vector ranges, and their geographic distribution. In this study, we intend to investigate wild and domestic ruminants for ticks and for tick-borne pathogens of the genus Babesia, Theileria, Anaplasma and Ehrlichia. One of our aims is to clarify the situation in wildlife and domestic animals by studying the host and the vector ranges of these pathogens, including ticks, as well as their geographic distribution. This information is essential to optimize cattle and wildlife management strategies especially in the context of translocation of both wild and domestic animals. These data are the basis for any other further studies on for example the influence of climate on the geographic distribution of these ticks and pathogens, in the context of global climate changes. The second aim specifically targets two pairs of tick and Babesia species that are currently competing in the studied area. This part of our project is aimed at capturing and comparing the population genetics features of both the invasive and out-competed ticks (e.g., effective population sizes and potential changes in demography, migration/drift balance among domestic and wild hosts, reproduction patterns etc) as well as précising the outputs of their competition relatively to the Babesia-related threats. The invasive tick is Rhipicephalus (Boophilus) microplus. Introduced to South Africa from Asia, it is the unique vector of the emerging pathogen, Babesia bovis in South Africa as well as a potential vector of other tick-borne pathogens such as B. bigemina, the agent of the African heartwater. Our recent results evidenced that R. (B.) microplus is still spreading in the country. The associated B. bovis species is very virulent and its emergence creates new epidemiological situations in some parts of the country. The resulting disease, called Asiatic redwater, is one of the most important livestock diseases from an economic point of view. Along its invasion, R. (B.) microplus is also displacing the native tick R. (Boophilus) decoloratus that is a good vector of B. bigemina but not of B. bovis. Combining a survey of these two Babesia species among wild and domestic ruminants with their prevalence in ticks and a clear understanding of the population dynamics of the competing Rhipicephalus (Boophilus) vectors within and among the domestic and wild host-compartments is a prerequisite to any forecast regarding the epidemiological emergence of Asiatic redwater, and hence to the evaluation of potential measures of protection of domestic and wild animals. Depending on the number of Babesia samples from each species collected in ticks, this study can later on be completed by an analysis in the selection pressures defined by the competitive tick vectors onto B. bigemina and by R. (B.) microplus onto B. bovis. To increase our knowledge on tick-borne pathogens and on their vectors, regarding their host range and geographic distribution and to clarify the current situation in wildlife and domestic animals, we will collect ticks and tissue (blood and/or organs) samples from wild and domestic animals in parks and farms where these animal groups have contacts with each other. Ticks and host tissues will be analysed for the tick-borne pathogens mentioned above using PCR followed by Reverse Line Blotting. In addition, Giemsa stained blood smears will allow visualisation of the infections in the blood of hosts. To monitor the displacement of R. (B.) microplus and the highly virulent B. bovis pathogen into new areas in South Africa, more precisely in the Free State and the North West Provinces, we will investigate the borders between areas where R. (B.) microplus is known to occur and areas where this tick species has not been described yet. The population genetics analyses of that tick and of the out-competed R. (B.) decoloratus will be performed using the polymorphism of microsatellite markers. Our collaborators in Montpellier, France have already developed microsatellite markers for R. (B.) microplus (Koffi et al. 2006a) and have already used their polymorphism to characterise the population genetics characteristics of its invasion into New Caledonian Island (Koffi et al. 2006b, Chevillon et al. 2007). They will help in developing accurate markers for R. (B.) decoloratus, additional ones in R. (B.) microplus if those already developed are found monomorphic in South Africa as well as in genotyping ticks and training us in population genetic analyses. The fieldwork will be carry out in the Free State and North West Provinces of South Africa. Samples (ticks and host tissues (blood and/or organs)) will be analysed at the University of Neuchâtel. Contacts with a scientific South African collaborator, as well as with farmers, veterinarians and a game capture team have been already established in a previous study (Tonetti et al., submitted) in the Free State.
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