Call for Caution to Consider Lyme Neuroborreliosis as A Frequent Neurological Disease in Mexico

Epidemiology of Lyme Disease

Lyme disease is the most common vector-borne illness in North America and Europe. The etiologic agent, Borrelia burgdorferi sensu lato, is transmitted to humans by certain species of Ixodes ticks, which are found widely in temperate regions of the Northern hemisphere. Clinical features are diverse but death is rare. The risk of human infection is determined by the distribution and abundance of vector ticks, ecologic factors influencing tick infection rates, and human behaviors that promote tick bite. Rates of infection are highest among children aged 5 to 15 years and adults aged more than 50 years. In the northeastern United States where disease is most common, exposure occurs primarily in areas immediately around the home. Knowledge of disease epidemiology is important for patient management and proper diagnosis.

Genetic diversity of Borrelia burgdorferi sensu stricto: Novel strains from Mexican wild rodents

Borrelia burgdorferi s.s. is a Gram-negative spirochaete, the aetiological agent of Lyme disease, the most common vector-borne disease in the Northern hemisphere. Reports on the presence of B. burgdorferi in central Mexico have been strongly criticized, since these were based only on unspecific serological methods. Furthermore, the worldwide genetic diversity of B. burgdorferi s.s. has not been evaluated. For this reason, the aim of the present study was to confirm the presence of B. burgdorferi in the central area of Mexico and to evaluate its relationship with regard to the global genetic diversity of B. burgdorferi s.s. To achieve this, fragments of the flagellin and the outer surface protein A genes were amplified from ear biopsies of the arboreal wild endemic mice Habromys schmidlyi. With these sequences, a concatenated Bayesian analysis was performed to confirm the identity of B. burgdorferi s.s. Afterwards, the global genetic diversity of this bacterial species was evaluated using our sequences and those available in GenBank. A prevalence of 10.4% (5/48) of H. schmidlyi infected with Borrelia sp. was detected, and the phylogenetic analyses confirmed the identity of B. burgdorferi s.s. Using both genes, the genetic diversity was low. However, genetic structuring analyses revealed that populations of western United States and those from Mexico formed slightly different genetic groups, separated from the populations of the rest of the world. Our study not only confirms the presence of this bacterium in central Mexico, but also shows the most southern record of this bacterium so far. It also highlights the importance of H. schmidlyi as a new potential host of this bacterial species. Our study also provides first genetic data on an incipient process of divergence in B. burgdorferi s.s. populations of eastern United States and central Mexico.

Borrelia in neotropical bats: Detection of two new phylogenetic lineages

The genus Borrelia encompasses 50 spirochetal species, several of which are pathogenic and have been detected in a wide range of mammals, especially rodents and cervids. Although the order Chiroptera is the second most diverse mammalian order, and borreliosis represents a human and veterinary health problem in endemic countries, few studies have previously reported infections of Borrelia in these flying mammals. For this reason, the aim of the present study was to detect the presence of, and to analyze the diversity of Borrelia species in several bat species from Mexico. A total of 69 bats belonging to 11 species were collected and molecular detection of Borrelia was performed by amplifying three genes using specific primers. Only five individuals of four bat species (Saccopteryxbilineata, Choeroniscus godmani, Sturnira parvidens and Lasiurus cinereus) tested positive for Borrelia DNA. We now show the first Borrelia record in Mexican bats from two different ecosystems, where previously several potential vector species of the genus Ixodes and Ornithodoros had been reported. The Borrelia sequences obtained from the bats revealed two new putative lineages, one from the relapsing fever group and the second one belonging to the Borrelia burgdorferi s.l. complex, both of which are related to zoonotic species. These results highlight the importance of bats as potential hosts of Borrelia, and the imperative need of active surveillance in flying mammals in order to understand their potential role in the life cycle of this bacteria genus.

Lyme disease and relapsing fever in Mexico: An overview of human and wildlife infections

Lyme borreliosis and Relapsing fever are considered emerging and re-emerging diseases that cause major public health problems in endemic countries. Epidemiology and geographical distribution of these diseases are documented in the US and in Europe, yet in Mexico, studies are scarce and scattered. The aims of this study were (1) to present the first confirmatory evidence of an endemic case of Lyme disease in Mexico and (2) to analyze the epidemiological trend of these both diseases by compiling all the information published on Borrelia in Mexico. Two databases were compiled, one of human cases and another of wild and domestic animals in the country. The analysis included the evaluation of risk factors for the human population, the diversity of Borrelia species and their geographic distribution. Six Borrelia species were reported in a total of 1,347 reports, of which 398 were of humans. Women and children from rural communities were shown to be more susceptible for both Lyme borreliosis and Relapsing fever. The remaining reports were made in diverse mammalian species and ticks. A total of 17 mammalian species and 14 tick species were recorded as hosts for this bacterial genus. It is noteworthy that records of Borrelia were only made in 18 of the 32 states, mainly in northern and central Mexico. These results highlight the importance of performing further studies in areas where animal cases have been reported, yet no human studies have been done, in order to complete the epidemiological panorama for Lyme borreliosis and Relapsing fever. Finally, the search for Borrelia infections in other vertebrates, such as reptiles and amphibians is recommended to gain a more accurate view of Borrelia species and their distribution. The geographical approach presented herein justifies an intense sampling effort to improve epidemiological knowledge of these diseases to aid vector control and prevention programs.