Rickettsia parkeri (Rickettsiales: Rickettsiaceae) detected in Amblyomma maculatum ticks collected on dogs in Tabasco, Mexico.

The present study was carried out to identify Rickettsia species with zoonotic potential in ticks collected from dogs in a rural area in Tabasco, Mexico. In total 197 Amblyomma maculatum ticks were collected from 40 domestic dogs. The collected specimens were pooled and subjected to DNA extraction. A fragment (380 bp) of citrate synthase gene (gltA) was amplified by polymerase chain reaction (PCR) using universal primers for Rickettsia. A second PCR was later performed to amplify a fragment (420 bp) of the outer membrane protein B gene (ompB). The PCR products were purified, sequenced and compared using the basic local alignment search tool (BLAST). Twenty out of 40 (50%) tick pools assayed were positive for rickettsial DNA using both primer pairs. The consensus sequence obtained from the ompB gene fragments showed 99.5-100% of identity with strains of Rickettsia parkeri. This study provides the first molecular evidence of the presence of R. parkeri in A. maculatum ticks infesting domestic dogs from southeastern Mexico. Close contact between dogs and humans should lead to consider the infection caused by this species of Rickettsia among the differential diagnoses for people of Tabasco, Mexico, who show acute febrile syndrome associated to inoculation eschar and have a clinical history of tick exposure.

Molecular detection of Dirofilaria immitis in dogs and mosquitoes in Tabasco, Mexico.

BACKGROUND & OBJECTIVES: Dirofilaria immitis is a filarial nematode that causes heartworm disease in domestic as well as wild canines and felines; and cutaneous or pulmonary infections in humans. The purpose of the study was to estimate the prevalence of D. immitis in domestic dogs in Tabasco, Mexico and to assay mosquitoes temporally and spatially associated with dogs for evidence of infection. METHODS: Blood was collected from 1050 dogs in 1039 houses during a random household survey performed in 2016 and 2017. Genomic DNA was extracted and assayed by polymerase chain reaction (PCR) using pan-filarial primers and various species-specific primers. Dog owners were interviewed using a structured questionnaire designed to collect information on factors that may impact the occurrence of filarial infection. The association between canine dirofilariasis prevalence and factors likely to impact infection was determined by univariate logistic regression analysis, followed by multivariate binomial logistic regression analysis. Indoor and outdoor resting mosquitoes were collected from houses by manual aspiration. Mosquitoes were identified according to species, homogenized and tested by PCR for filarial nematodes. RESULTS: A total of 84 (8%) dogs were positive for D. immitis DNA, while 3 (0.3%) dogs contained Acanthocheilonema reconditum DNA. Several factors were significantly associated with D. immitis infection. For example, dogs that lived <100 m from a large source of open standing water were significantly more likely (p = 0.002) to become infected with D. immitis than other dogs. Additionally, dogs with infrequent or no anthelmintic treatment were significantly more likely (p = 0.0) to become infected than dogs that were regularly treated. The entomologic investigation yielded 2618 female mosquitoes from 14 species. Four pools of Culex quinquefasciatus were positive for D. immitis DNA and the minimum infection rate, calculated as the number of positive pools per 1000 mosquitoes tested, was 2.9. INTERPRETATION & CONCLUSION: The study identified several factors positively associated with an increased risk of D. immitis infection in domestic dogs in Tabasco and provides evidence that Cx. quinquefasciatus is potentially an important vector in this region. This information can be used by local veterinarians and dog owners to reduce the burden of D. immitis on canine health.