Bouyer, D. H. | Search bioRxiv

bioRxiv2023

Science abhors a surveillance vacuum: detection of ticks and tick-borne bacteria in southern New Mexico through passive surveillance

Robust tick surveillance enhances diagnosis and prevention of tick-borne pathogens, yet surveillance efforts in the U.S. are highly uneven, resulting in large surveillance vacuums, one of which spans the state of New Mexico. As part of a larger effort to fill this vacuum, we conducted both active and passive tick sampling in New Mexico, focusing on the southern portion of the state. We conducted active tick sampling using dragging and CO2 trapping at 45 sites across Hidalgo, Dona Ana, Otero, and Eddy counties periodically between June 2021 and August 2022. We also conducted opportunistic, passive tick sampling in 2021 and 2022 from animals harvested by hunters or captured or collected by researchers and animals housed in animal hospitals, shelters, and farms. All pools of ticks were screened for Rickettsia rickettsii, R. parkeri, R. amblyommatis, Ehrlichia ewingii, and E. chaffeensis. Active sampling yielded no ticks. Passive sampling yielded 497 ticks comprising Carios kelleyi from pallid bats, Rhipicephalus sanguineus from dogs, mule deer, and Rocky Mountain elk, Otobius megnini from dogs, cats, horses, and Coues deer, Dermacentor parumapertus from dogs and black-tailed jackrabbits, D. albipictus from domesticated cats, mule deer and Rocky Mountain elk, and Dermacentor spp. from American black bear, Rocky Mountain elk, and mule deer. One pool of D. parumapterus from a black-tailed jackrabbit in Luna County tested positive for R. parkeri, an agent of spotted fever rickettsiosis. Additionally, a spotted fever group Rickettsia was detected in 6 of 7 Carios kelleyi pools. Two ticks showed morphological abnormalities; however, these samples did not test positive for any of the target pathogens, and the cause of the abnormalities is unknown. Passive surveillance yielded five identified species of ticks from three domestic and six wild mammal species. One tick pool from a black-tailed jackrabbit was found to harbor Rickettsia parkeri, and six pools of Carios kelleyi ticks, argasid ticks that have been reported to bite humans, were found to harbor a spotted fever group Rickettsia. Our findings update tick distributions and inform the public, medical, and veterinary communities of the potential tick-borne pathogens present in southern New Mexico.

zoology↗

bioRxiv2018

A biosafety level-2 dose-dependent lethal mouse model of spotted fever rickettsiosis: Rickettsia parkeri Atlantic Rainforest-like isolate

BackgroundThe species of the Rickettsia genus is separated into four groups: the ancestral group, typhus group, transitional group and spotted fever group. Rickettsia parkeri, a spotted fever group Rickettsia, has been reported across the American continents as infecting several tick species and is associated with a relatively mild human disease characterized by eschar formation at the tick feeding site, fever, myalgia and rash. Currently several mouse models that provide a good approach to study the acute lethal disease caused by Rickettsia, but these models can only be performed in an animal biosafety level 3 laboratory. We present an alternative mouse model for acute lethal rickettsial disease, using R. parkeri and C3H/HeN mice, with the advantage that this model can be studied in an animal biosafety level 2 laboratory.\n\nPrincipal findingsIn the C3H/HeN mouse model, we determined that infection with 1 x 106 and 1 x 107 viable R. parkeri Atlantic Rainforest-like isolate produced dose-dependent severity, whereas infection with 1 x 108 viable bacteria resulted in a lethal illness. The animals became moribund on day five or six post-infection. The lethal disease was characterized by ruffled fur, erythema, labored breathing, decreased activity, and hunched back, which began on day three post-infection (p.i.) and coincided with the peak bacterial loads. Significant splenomegaly (on days three and five p.i.), neutrophilia (on days three and five p.i.), and thrombocytopenia (on days one, three and five p.i.) were observed.\n\nSignificanceThe greatest advantage of this inbred mouse model is the ability to investigate immunity and pathogenesis of rickettsiosis with all the tools available at biosafety level 2.\n\nAuthor summaryRickettsia is a bacterial genus that contains distinct species that are transmitted by arthropods. Many of these agents produce infection and disease in humans. The illness can range from very aggressive, such as Rocky Mountain spotted fever caused by Rickettsia rickettsii, to mild human disease characterized by eschar formation at the tick feeding site and less severe symptoms caused by Rickettsia parkeri. To study these diseases, animal models are invaluable, and mouse models offer the best advantages. Several mouse models are most useful for study of the acute lethal disease produced by these bacteria, providing the opportunity to test different treatments and vaccine candidates. However, work with these models requires an animal biosafety level 3 laboratory. In this report, we present an alternative mouse model to study acute lethal spotted fever group rickettsial disease with the advantage that experiments can be performed at biosafety level 2.

pathology↗