Plasmodium vivax and Mansonella ozzardi co-infection in north-western Argentina.

A case of co-infection with Plasmodium vivax and Mansonella ozzardi was detected in a blood sample from a person who had shown symptoms of malaria and lived in a city that was close to the Argentina/Bolivia border. The case was detected during a random revision of thick and thin smears from patients diagnosed with malaria from various towns and cities located in north-western Argentina between 1983 and 2001. Trophozoites of P. vivax were observed in the thin blood smear along with M. ozzardi microfilaria (larval form), which presented a long, slender, pointed anucleate tail and the absence of the sheath. This last characteristic is shared with Mansonella perstans, Mansonella streptocerca and Onchocerca volvulus. More rigorously controlled studies to detect other co-infection cases in the area as well as the possibility of importation from Bolivia into Argentina are currently ongoing. The relationship between the malaria parasite and microfilaria, the potential effect of malaria treatment on the development of M. ozzardi, and the possible impact of this microfilaria on the immunity of a person against P. vivax are all still unknown. This contribution constitutes a point of focus for future studies involving the interaction between the parasites and the potential risk that humans are exposed to.

Mansonella ozzardi in Neotropical region of Argentina: Prevalence through time (1986-2010).

Human filariasis caused by Mansonella ozzardi is a parasitic infection of a controversial pathology and poorly studied in Argentina. The aim of this study was not only to obtain data of the prevalence of M. ozzardi in Northwestern Argentina through comparison of infection rates in relation to sex and age group determining the range of distribution of mansonelliasis in the region but also to investigate the prevalence of the cases over time. Through field work carried between 1986 and 2010 by technicians of the National Ministry of Health, aiming to detect active cases of malaria in the Northwestern Argentina, blood samples were taken for smear and thick blood. 417 blood samples were examined, 381 of them (91.4%) were positive for M. ozzardi. The highest prevalence was found in Salta province (92.3%) mainly affecting the male sex (92.6%) and the age groups comprised between 48-57 years (97.0%) and ≥ 68 (90.7%). The paired t-test and Spearman coefficients showed significant differences in prevalence according to sex (t=2.677; p=0.015), and according infection rates in males and females/age (r=0.994; p=0.001; r=0.994, p=0.001, respectively). The prevalence over time showed a general pattern with the highest cases in 1986, decreasing later during the following years. Aguas Blancas, El Oculto and San Ramón de la Nueva Orán, exhibited a pattern of prevalence according to the general trend but Salvador Mazza and Tartagal, which are also localities close to the border with Bolivia, showed peaks of cases up to 2010. These results provide relevant information about M. ozzardi in Argentina, demonstrating not only its presence and endemicity after almost 100 years from its discovery in the country, but also its wide range of distribution in the region.

Demographic history and population structure of Anopheles pseudopunctipennis in Argentina based on the mitochondrial COI gene.

BACKGROUND: Anopheles pseudopunctipennis is an important malaria vector in the Neotropical region and the only species involved in Plasmodium transmission in the Andean foothills. Its wide geographical distribution in America, high preference for biting humans and capacity to rest inside dwellings after feeding, are attributes contributing to its vector status. Previous reports have tried to elucidate its taxonomic status, distinguishing populations from North, Central and South America. In the present study we used a mitochondrial marker to examine the demographic history of An. pseudopunctipennis in northwestern Argentina. METHODS: Twelve localities were selected across 550 km of the distribution of this species in Argentina, including two near the Bolivian border and several in South Tucumán, for sampling. A fragment of the cytochrome oxidase I (COI) gene was sequenced and haplotype relationships were analyzed by a statistical parsimony network and a Neighbor-Joining (NJ) tree. Genetic differentiation was estimated with FST. Historical demographic processes were evaluated using diversity measures, neutrality tests and mismatch distribution. RESULTS: Forty-one haplotypes were identified, of which haplotype A was the most common and widely distributed. Neither the network nor the NJ tree showed any geographic differentiation between northern and southern populations. Haplotype diversities, Tajima's DT and Fu & Li's F and D neutrality tests and mismatch distribution supported a scenario of Holocene demographic expansion. CONCLUSION: The demographic pattern suggests that An. pseudopunctipennis has undergone a single colonization process, and the ancestral haplotype is shared by specimens from all localities, indicating mitochondrial gene flow. Genetic differentiation was minimal, observed only between one northern and one southern locality. The estimated time of the population expansion of this species was during the Holocene. These data suggest that regional vector control measures would be equally effective in both northern and southern localities sampled, but also that insecticide resistant genes may spread rapidly within this region.