Influenza A virus antibodies in dogs, hunting dogs, and backyard pigs in Campeche, Mexico.

AIMS: This study aimed to identify exposure to human, swine, and avian influenza A virus subtypes in rural companion and hunting dogs, backyard pigs, and feral pigs. METHODS AND RESULTS: The study took place in a region of southeastern Mexico where the sampled individuals were part of backyard production systems in which different domestic and wild species coexist and interact with humans. We collected blood samples from pigs and dogs at each of the sites. We used a nucleoprotein enzyme-linked immunosorbent assay to determine the exposure of individuals to influenza A virus. Haemagglutination inhibition was performed on the positive samples to determine the subtypes to which they were exposed. For data analysis, a binomial logistic regression model was generated to determine the predictor variables for the seropositivity of the individuals in the study. We identified 11 positive individuals: three backyard pigs, four companion dogs, and four hunting dogs. The pigs tested positive for H1N1 and H1N2. The dogs were positive for H1N1, H1N2, and H3N2. The model showed that dogs in contact with backyard chickens are more likely to be seropositive for influenza A viruses. CONCLUSIONS: We demonstrated the essential role hunting dogs could play as intermediate hosts and potential mixing vessel hosts when exposed to human and swine-origin viral subtypes. These results are relevant because these dogs interact with domestic hosts and humans in backyard systems, which are risk scenarios in the transmission of influenza A viruses. Therefore, it is of utmost importance to implement epidemiological surveillance of influenza A viruses in backyard animals, particularly in key animals in the transmission of these viruses, such as dogs and pigs.

Molecular detection of Rickettsia amblyommatis and Rickettsia parkeri in ticks collected from wild pigs in Campeche, Mexico.

Tick-borne rickettsioses are caused at least by 15 species of Rickettsia of the Spotted fever group, which represent a major emerging and re-emerging public health problem worldwide. Some of these microorganisms have complex cycles involving the interaction of multiple species of ticks and wild and domestic mammals. Rickettsia infection was investigated in ticks collected from wild pigs at six localities in southeastern Mexico. We collected and tested 196 ticks belonging to four species, including Amblyomma maculatum, Amblyomma mixtum, Amblyomma ovale and Riphicephalus microplus, from 13 of 20 (65%) wild pigs sampled. Overall, Rickettsia DNA was detected in 13.8% of ticks tested (10 ♂ and 17 ♀). Of the 27 Rickettsia-positive ticks, six were A. maculatum, and 21 A. mixtum. Sequencing and phylogenetic analysis of the gltA and ompB genes revealed the presence of Rickettsia parkeri sensu stricto in one female A. maculatum and Rickettsia amblyommatis in five A. maculatum (2 ♂, 3 ♀) and 21 A. mixtum ticks (8 ♂, 13 ♀). The finding of two rickettsial agents in ticks collected from a wild pig population that is regularly captured and kept in captivity or hunted as a source of food raises concern about potential disease transmission to humans and domestic animals. However, more investigations are needed to further understand the ecology of Rickettsia species in free-ranging animals and their implications for human health.

Effects of landscape anthropization on sylvatic mosquito assemblages in a rainforest in Chiapas, Mexico.

Global change and ecosystem transformation at regional and local scales during recent decades have facilitated the exponential increase of outbreaks of mosquito-borne diseases. Mosquito-borne pathogens are responsible for millions of infections, mainly in tropical regions where marginalized human populations are located, and where in recent years processes of landscape anthropization have occurred. Anthropogenic landscape transformation is known to change species assemblages. However, the magnitude of these effects is largely unknown, and the effects of anthropogenic landscape transformation on sylvatic mosquito assemblages are poorly known in Mexican ecosystems. We evaluate how mosquito abundance, richness, and diversity change along a gradient of three human-modified landscapes-one highly anthropized, one moderately anthropized, and one slightly anthropized-within a tropical forest matrix in a Protected Natural Area in Chiapas. A total of 4 538 mosquitoes belonging to 23 species were captured and identified at the three sites. We found differences in the structure and abundance of the three mosquito assemblages. The species assemblage of the highly anthropized site was significantly different from the other sites, and the relative abundance of the assemblages increased with landscape anthropization. Our results suggest that landscape anthropization alters the composition and structure of mosquito assemblages, modifying the abundance and species richness of mosquitoes associated with sylvatic ecosystems. This could support the hypothesis of intermediate disturbance that suggests the diversity is maximized when late and early successional species coexist in these ecosystems. This information is essential to understand the ecology of potential sylvatic vectors and the environmental factors that are involved in the emergence and re-emergence of mosquito-borne diseases.

Eco-Epidemiological Evidence of the Transmission of Avian and Human Influenza A Viruses in Wild Pigs in Campeche, Mexico.

Influenza, a zoonosis caused by various influenza A virus subtypes, affects a wide range of species, including humans. Pig cells express both sialyl-α-2,3-Gal and sialyl-α-2,6-Gal receptors, which make them susceptible to infection by avian and human viruses, respectively. To date, it is not known whether wild pigs in Mexico are affected by influenza virus subtypes, nor whether this would make them a potential risk of influenza transmission to humans. In this work, 61 hogs from two municipalities in Campeche, Mexico, were sampled. Hemagglutination inhibition assays were performed in 61 serum samples, and positive results were found for human H1N1 (11.47%), swine H1N1 (8.19%), and avian H5N2 (1.63%) virus variants. qRT-PCR assays were performed on the nasal swab, tracheal, and lung samples, and 19.67% of all hogs were positive to these assays. An avian H5N2 virus, first reported in 1994, was identified by sequencing. Our results demonstrate that wild pigs are participating in the exposure, transmission, maintenance, and possible diversification of influenza viruses in fragmented habitats, highlighting the synanthropic behavior of this species, which has been poorly studied in Mexico.