Host-Parasite Relationship of Ticks (Acari: Ixodidae and Argasidae) and Feral Pigs (Sus scrofa) in the Nhecolandia Region of the Pantanal Wetlands in Mato Grosso do Sul

Feral pigs (S. scrofa) were introduced to the Pantanal region around 200 years ago and the population appears to be in expansion. Its eradication is considered to be impossible. The population of feral pigs in the Pantanal wetlands is currently estimated at one million. Two scientific excursions were organized. The first was conducted during the dry season, when 21 feral pigs were captured and the second was during the wet season, when 23 feral pigs were captured. Ticks were collected and the oviposition and hatching process were studied to confirm the biological success of each tick species. Three tick species were found to be feeding on feral pigs: Amblyomma cajennense, A. parvum, and Ornithodoros rostratus. During the dry season, 178 adult A. cajennense were collected, contrasting with 127 A. cajennense specimens in the wet season. This suggests that the seasonality of these ticks in the Brazilian Pantanal wetlands could be different from other regions. The results indicate that A. parvum and A. cajennense are biologically successful parasites in relation to feral pigs. A. cajennense appears to have adapted to this tick-host relationship, as well as the areas where feral pigs are abundant, and could play a role in the amplification of this tick population. 1. Introduction Ticks have coevolved with various wild animal hosts which are reservoir hosts for pathogens such as fungi, bacteria, viruses, rickettsiae, and protozoan which can be transmitted to domestic mammals and humans [1–3]. Ticks that feed on feral or domestic pigs (Sus scrofa) and their tick-borne diseases have been previously studied worldwide [4–7]. The most common tick species reported in association with domestic pigs in Brazil is Amblyomma cajennense (Fabricius, 1787), an eclectic tick that has a broad range of hosts and widespread distribution [8–10]. In Brazil, this hard tick is an important vector of Rickettsia rickettsii to humans [11]. A second genus reported in association with Brazilian pigs is the genus Ornithodoros, which has two species: O. rostratus and O. brasiliensis. Both of these species have also been reported in association with wild native pigs (Tayassu sp.) [8, 9]. The Pantanal ecosystem is considered to be one of the most well-preserved biomes in Brazil and was added to the UNESCO World Heritage List in 2000. The Brazilian Pantanal has been described as a “biological hotspot” for conservation and one of the richest and the most diverse ecosystems in the world. In this biome, wild animals and their parasites engage in complex and dynamic interactions. However, this