Background: On the American continent, Rhipicephalus sanguineus s.l. comprises two species: Rhipicephalus linnaei and R. sanguineus s.s. Each species has been identified as a potential vector of at least one of five species of pathogenic bacteria of the genus Rickettsia. In particular, Rickettsia massiliae is one of three species with the greatest importance in public health at the continental level. In Mexico, this species is reported exclusively in the Nearctic states of Baja California and Chihuahua.Aim: For this reason, the aim of this work was to provide new records of R. massiliae for the centre of the country derived from active acarological surveillance.Materials and Methods: During the period of February–October 2019, 29 dogs from six municipalities in the state of Morelos were sampled. Hosts were visually inspected, and ticks were recovered and identified morphologically and molecularly by amplification of the 16S rDNA gene. Subsequently, five genes from members of the genus Rickettsia were amplified and sequenced.Results: A total of 229 (117♀, 98♂ and 14 N) ticks identified as R. linnaei were recovered, two of which were positive for R. massiliae strains related to those recovered from Argentina and the United States.Conclusions: This work provides the second record of R. massiliae infecting R. linnaei in Mexico and the Americas, increasing the geographic distribution of this Rickettsia species in the Neotropical region, and providing information on the possible role of R. linnaei as a potential vector of this microorganism.

El loxoscelismo es ocasionado cuando el veneno dermonecrótico producido por las arañas del género Loxosceles, conocidas como “arañas violinistas”, ingresa al organismo de una persona a través de su mordida. En México ocurre un subregistro de los casos de loxoscelismo por la ausencia de pruebas de laboratorio para su diagnóstico y la dificultad del cuadro clínico. El objetivo de este trabajo es describir un caso de loxoscelismo cutáneo ocasionado por mordedura de Loxosceles yucatana en un residente de Yucatán, México. El loxoscelismo cutáneo es el tipo más frecuente y menos severo. El presente caso se diagnosticó por medio de la sintomatología registrada en la historia clínica, la lesión inicial y la identificación de arañas L. yucatana. Este trabajo representa la primera descripción de un caso de loxoscelismo cutáneo con resolución favorable en Yucatán.

In the state of Sonora, the bite of the spiders Latrodectus mactans, Latrodectus geometricus and Latrodectus hesperus, can cause serious health complications due to their toxicity. To characterize the conditions under which poisonings by Latrodectus spider bites occurred. Retrospective descriptive study of confirmed cases of poisoning by Latrodectus spider bites that occurred in municipalities of Sonora from 2021 to 2024. 65 cases of Latrodectus bites were obtained (52.3% men, 47.7% women). The 78.5% of the cases occurred in the home and 44.6% were recorded in bedrooms, the right lower limb was the most frequent anatomical area for bites (32.3%). Of the recorded cases, 98.5% presented some degree of poisoning and 1.5% were asymptomatic. The most frequent symptoms were intense pain (87.5%), itching (54.7%), and local edema (50.0%). The 68.8% of the poisoned individuals required one bottle of faboterápico for treatment. Latrodectus bites occurred mostly in men, primarily in bedrooms at home while they were resting. The lesions were located primarily on the right lower and upper limbs (63.1%), and during the study period, 84.6% of the 65 reported cases received treatment, with no deaths reported.