The Evolving Medical and Veterinary Importance of the Gulf Coast tick (Acari: Ixodidae)

Abstract

Amblyomma maculatum Koch (the Gulf Coast tick) is a three-host, ixodid tick that is distributed throughout much of the southeastern and south-central United States, as well as several countries throughout Central and South America. A considerable amount of scientific literature followed the original description of A. maculatum in 1844; nonetheless, the Gulf Coast tick was not recognized as a vector of any known pathogen of animals or humans for >150 years. It is now identified as the principal vector of Hepatozoon americanum, the agent responsible for American canine hepatozoonosis, and Rickettsia parkeri, the cause of an emerging, eschar-associated spotted fever group rickettsiosis identified throughout much of the Western Hemisphere. Coincident with these discoveries has been recognition that the geographical distribution of A. maculatum in the United States is far more extensive than described 70 yr ago, supporting the idea that range and abundance of certain tick species, particularly those with diverse host preferences, are not fixed in time or space, and may change over relatively short intervals. Renewed interest in the Gulf Coast tick reinforces the notion that the perceived importance of a particular tick species to human or animal health can be relatively fluid, and may shift dramatically with changes in the distribution and abundance of the arthropod, its vertebrate hosts, or the microbial agents that transit among these organisms.

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

“…During 2004-2015, at least 40 patients with R. parkeri rickettsiosis were identified from 10 states (35-41) (CDC, unpublished data, 2015). The median age of patients from case reports was 53 years (range: 23-83 years) (38); R. parkeri rickettsiosis has not been documented in children, and no fatal cases have been reported. R. parkeri is transmitted by the Gulf Coast tick, Amblyomma maculatum ( Figure 9).…”

“…Regional lymphadenopathy is detected in approximately 25% of patients. Gastrointestinal manifestations, such as nausea or vomiting, are rare (38,39). Mild thrombocytopenia has been observed in 40%, mild leukopenia in 50%, and modest elevation of hepatic transaminase levels in 78% of cases (39).…”

“…For example, R. rickettsii infection can be acquired in Canada and Mexico, as well as in Central America and South America, where cases are reported from Costa Rica, Panama, Brazil, Colombia, and Argentina (253)(254)(255)(256)(257)(258)(259)(260). R. parkeri infections have been described in Uruguay, Brazil, and Argentina (38,253,261,262). Human anaplasmosis has been reported from several countries throughout Europe (263), as well as from several Asian countries, including China, Korea, Russia, and Japan (264)(265)(266)(267).…”

Expanding Range of Amblyomma americanum and Simultaneous Changes in the Epidemiology of Spotted Fever Group Rickettsiosis in the United States

“…12 The Gulf Coast tick is an aggressive biter of humans, and the prevalence of R. parkeri in the Gulf Coast tick is often > 20%. 46 Despite its name, the range of the Gulf Coast tick has expanded beyond the coast of the Gulf of Mexico. 47 Our results suggest a contribution of the Gulf Coast tick to the national statistics for SFG rickettsiosis.…”

“…This finding is more consistent with R. parkeri rickettsiosis than with either RMSF or infections with less pathogenic SFG Rickettsia species, suggesting the importance of R. parkeri and its vector may be underappreciated. 46 In Kansas and Oklahoma, the Gulf Coast tick may not carry R. parkeri because of high prevalence of "Candidatus Rickettsia andeanae", an agent of unknown human pathogenicity. 48 In our results, the HR in Kansas and Oklahoma was lower than other parts of the Gulf Coast tick's range, suggesting that the Gulf Coast tick may not be a vector associated with severe SFG rickettsiosis in these states.…”