Ecology, biology and distribution of spotted-fever tick vectors in Brazil

Abstract

Spotted-fever-caused Rickettsia rickettsii infection is in Brazil the major tick-borne zoonotic disease. Recently, a second and milder human rickettsiosis caused by an agent genetically related to R. parkeri was discovered in the country (Atlantic rainforest strain). Both diseases clearly have an ecological background linked to a few tick species and their environment. Capybaras (Hydrochoerus hydrochaeris) and Amblyomma cajennense ticks in urban and rural areas close to water sources are the main and long-known epidemiological feature behind R. rickettsii-caused spotted-fever. Unfortunately, this ecological background seems to be increasing in the country and disease spreading may be foreseen. Metropolitan area of São Paulo, the most populous of the country, is embedded in Atlantic rainforest that harbors another important R. rickettsii vector, the tick Amblyomma aureolatum. Thus, at the city–forest interface, dogs carry infected ticks to human dwellings and human infection occurs. A role for R. rickettsii vectoring to humans of a third tick species, Rhipicephalus sanguineus in Brazil, has not been proven; however, there is circumstantial evidence for that. A R. parkeri-like strain was found in A. ovale ticks from Atlantic rainforest and was shown to be responsible for a milder febrile human disease. Rickettsia-infected A. ovale ticks are known to be spread over large areas along the Atlantic coast of the country, and diagnosis of human infection is increasing with awareness and proper diagnostic tools. In this review, ecological features of the tick species mentioned, and that are important for Rickettsia transmission to humans, are updated and discussed. Specific knowledge gaps in the epidemiology of such diseases are highlighted to guide forthcoming research.

Serologic evidence of the exposure of small mammals to spotted-fever Rickettsia and Rickettsia bellii in Minas Gerais, Brazil

“…This apparent disconnection of environmental and host infestation may be explained by limitations of the sampling method of the environment, differing microenvironmental preferences of the host and parasite, and/or the lack of attraction of these small mammal species to specific ticks. In fact, A. cajennense sensu lato in Brazil are known to feed mainly on large mammals such as horses and capybaras in the adult stage [23]. Further, samplings by cloth dragging, which were restricted to mornings, as well as temperature variations may have caused sampling bias with reflections on tick species and numbers collected.…”

Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States

“…More recently, the brown dog tick, Rhipicephalus sanguineus ( Figure 6), which is located throughout the United States (Figure 7), has been recognized as an important vector in parts of Arizona (16) and along the U.S.-Mexico border. Several tick species of the genus Amblyomma are vectors of R. rickettsii from Mexico to Argentina, including A. cajennense, A. aureolatum, A. imitator, and A. sculptum (19)(20)(21)(22). Although the geographic ranges of A. imitator and A. mixtum (a species closely related to A. cajennense) extend into Texas, the role of Amblyomma ticks in transmission of R. rickettsii in the United States has not been established.…”

Probability of occurrence of the Brazilian spotted fever in northeast of Paraná state, Brazil

“…Moreover, not only A. sculptum is responsible for transmitting BSF but other species of ticks may also play a role (e.g. A. ovale and A. triste) (SABATINI et al, 2010;SZABÓ et al, 2013;BARBIERI et al, 2014;MONJE et al, 2016).…”