Bartonella Species in Cambodia, Ghana, Laos, and Peru: Results from Vector and Serosurveys.

Background: Bartonella species are fastidious gram-negative vector-borne bacteria with a wide range of mammalian reservoirs. While it is understood that some species of Bartonella are human pathogens, the extent of human exposure to Bartonella species (both pathogenic and nonpathogenic) is yet to be fully understood. Materials and Methods: To this end, residual sera from participants enrolled in undifferentiated fever studies in Cambodia, Ghana, Laos, and Peru were screened for the presence of IgG antibodies against Bartonella quintana and Bartonella henselae, using the FOCUS diagnostics Dual Spot- Bartonella IgG Immunofluorescence assay. Forty-eight patients with suspected or confirmed Bartonella bacilliformis exposure or infection in Peru were screened to assess cross-reactivity of the FOCUS assay for IgG against other Bartonella species. Results: Ten of 13 patients with confirmed B. bacilliformis infection were Bartonella-specific IgG positive, and overall, 36/48 of the samples were positive. In addition, 79/206, 44/200, 101/180, and 57/100 of the samples from Peru, Laos, Cambodia, and Ghana, respectively, were Bartonella-specific IgG positive. Furthermore, ectoparasite pools from Cambodia, Laos, and Peru were tested using quantitative real-time PCR (qPCR) for the presence of Bartonella DNA. Of the sand fly pools collected in Peru, 0/196 were qPCR positive; 15/140 flea pools collected in Cambodia were qPCR positive; while 0/105 ticks, 0/22 fleas, and 0/3 louse pools collected in Laos tested positive for Bartonella DNA. Conclusion: Evidence of Bartonella in fleas from Cambodia supports the possibility that humans are exposed to Bartonella through this traditional vector. However, Bartonella species were not found in fleas, ticks, or lice from Laos, or sand flies from Peru. This could account for the lower positive serology among the population in Laos and the strictly localized nature of B. bacilliformis infections in Peru. Human exposure to the Bartonella species and Bartonella as a human pathogen warrants further investigation.

Distribution of Triatoma dimidiata sensu lato (Reduviidae: Triatominae) and Risk Factors Associated with Household Invasion in Northern Belize, Central America.

To date, Triatoma dimidiata sensu lato [Reduviidae: Triatominae (Latreille 1811)] remains the sole vector species associated with Chagas disease transmission reported from Belize. Human infection data are limited for Belize and the disease transmission dynamics have not been thoroughly investigated, yet the likelihood of autochthonous transmission is supported by the widespread collection of infected vectors from within local households. Here, we report updated infection rates of the vector population and infestation rates for villages in north and central Belize. Overall, 275 households were enrolled in an ongoing vector surveillance program. Of the 41 insects collected, 25 were PCR positive for T. cruzi, indicating an infection rate as high as 60%. To further characterize the epidemiological risk of human-vector contact, determinants of household invasion were modeled. Local households were surveyed and characterized with respect to over 25 key factors that may be associated with household infestation by T. dimidiata s.l. While final models were not strongly predictive with respect to the risk factors that were surveyed, likely due to the low number of collection observations, the presence of domestic/peri-domestic dogs, nearby light sources, and household structure materials could be the focus of continued risk assessments. In northern Belize, this vector survey lends support to T. dimidiata s.l. inhabiting sylvatic settings as opposed to the classical paradigm of domiciliated vector populations. This designation has strong implications for the local level of human exposure risk which can help guide vector surveillance and control resources.

Distribution of Triatoma dimidiata sensu lato (Reduviidae: Triatominae) and Risk Factors Associated with Household Invasion in Northern Belize, Central America

The triatomine vectors (Hemiptera: Reduviidae) responsible for the transmission of Chagas disease are widely prevalent from the southern United States southward throughout much of Central and South America, ending in southern Argentina and Chile. Across this broad region, several important vector species serve as the main mode of transmission of Trypanosoma cruzi, the causative parasite of Chagas disease, to human hosts. Belize, a country in Central America, has reported the presence of a competent, infected vector species and limited instances of human disease. While several factors influencing vector presence have been described in the southern districts of Belize, the species distribution and associated attributes of household invasion in the north had not been investigated. Here, we compare methods for surveillance of triatomine vectors within households of northern and central Belize. The only vector species recorded, T. dimidiata, was designated sylvatic in nature, having strong implications for further ix surveillance and control strategies. Surveys targeting 20 ecological and social attributes associated with local households were modeled to determine association with T. dimidiata invasion. The final multivariate regression model developed from this data determined that T. dimidiata invasion was associated with the presence of peridomestic animals and proximity of community light sources. Because the presence data of triatomine vectors in Belize are scarce, ecological niche models were developed with source data from neighboring countries of Central America. Presence data from the region were modeled with respect to altitude and climate data layers to develop predictive maps for T. dimidiata and another important Central American vector, Rhodnius prolixus. Altitude and temperature profiles were both associated with the predicted presence of these common vector species. Initial assays for determining the effects of commonly used insecticides on colony-reared T. dimidiata are also described. There is some evidence that common control practices must be altered to achieve any effect on the target vector population. Collectively, the information gained from this research has direct bearing on surveillance and control of Chagas disease vectors in Belize, and may be used to strengthen ongoing efforts of local programs.