María J. Dantur Juri

The Spatio-Temporal Distribution Patterns of Biting Midges of the Genus Culicoides in Salta Province, Argentina

Abstract The goal of this survey was to analyze the spatio-temporal distribution patterns of Culicoides Latreille species (Diptera: Ceratopogonidae) and their relationship with environmental variables in Salta, northwestern Argentina. Culicoides were collected monthly from January 2003 through December 2005. The influence of the climatic variables on population abundance was analyzed with a multilevel Poisson regression. A total of 918 specimens belonging to five species were collected. The most abundant species was Culicoides paraensis Goeldi (65.5%), followed by Culicoides lahillei Iches (14.6%) and Culicoides debilipalpis Lutz (7.6%). The highest seasonal abundance for C. paraensis, C. debilipalpis and C. lahillei occurred during the spring and summer. A Poisson regression analysis showed that the mean maximum and minimum temperature and the mean maximum and minimum humidity were the variables with the greatest influence on the population abundance of Culicoides species.

First Report of Myiasis Caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in a Diabetic Foot Ulcer Patient in Argentina

Myiasis is usually caused by flies of the Calliphoridae family, and Cochliomyia hominivorax is the etiological agent most frequently found in myiasis. The first case of myiasis in a diabetic foot of a 54-year-old male patient in Argentina is reported. The patient attended the hospital of the capital city of Tucumán Province for a consultation concerning an ulcer in his right foot, where the larval specimens were found. The identification of the immature larvae was based on their morphological characters, such as the cylindrical, segmented, white yellow-coloured body and tracheas with strong pigmentation. The larvae were removed, and the patient was treated with antibiotics. The larvae were reared until the adults were obtained. The adults were identified by the setose basal vein in the upper surface of the wing, denuded lower surface of the wing, short and reduced palps, and parafrontalia with black hairs outside the front row of setae. The main factor that favoured the development of myiasis is due to diabetes, which caused a loss of sensibility in the limb that resulted in late consultation. Moreover, the poor personal hygiene attracted the flies, and the foul-smelling discharge from the wound favoured the females oviposition. There is a need to implement a program for prevention of myiasis, in which the population is made aware not only of the importance of good personal hygiene and home sanitation but also of the degree of implication of flies in the occurrence and development of this disease.

Spatial and Temporal Distribution of Culicoides insignis and Culicoides paraensis in the Subtropical Mountain Forest of Tucumán, Northwestern Argentina

ABSTRACT Culicoides insignis Lutz and Culicoides paraensis Goeldi are known bluetongue virus and filariasis (caused by Mansonella ozzardi Manson) vectors, respectively. Bluetongue virus appears to be restricted to northeastern Argentina, while filariasis is endemic in the subtropical mountain forest of the Argentine northwest. With the objective of characterizing the abundance and seasonality of both Culicoides species, entomological sampling was carried out from Dec 2004 to Nov 2005 in the southern area of the forest of Tucumán province. The specimens were captured using CO2-baited CDC light traps placed in 2 types of environments, wild and anthropized. The abundance of the specimens in relation to environmental variables was analyzed using multiple linear regression. Out of the 2,497 adult specimens collected, 76.9% belonged to C. paraensis, 20.4% to C. insignis and the 2.5% belonged jointly to Culicoides debilipalpis Lutz, Culicoides lahillei Lutz and Culicoides venezuelensis Mirsa & Ortiz (2.5%), and 0.2% could not be identified. Peaks of abundance of C. insignis and C. paraensis in decreasing magnitude were observed in the fall, summer and spring, respectively; and the largest number of specimens was found in the anthropized environment. Mean minimum and maximum temperatures and levels of accumulated rainfall were the variables that best explained the abundance of these 2 species. The present work is an important contribution not only to the knowledge of the spatial and temporal distribution and dynamics of these vectors in nature, but also to the elucidation of the implications of anthropization of the forest environment, and the effect of these climatic variables as determinants of the abundance of the species and, hence, as determinants of the possible transmission of filariasis in the subtropical mountain forest of the Argentine northwest.

Satellite-derived NDVI, LST, and climatic factors driving the distribution and abundance of Anopheles mosquitoes in a former malarious area in northwest Argentina

ABSTRACT: Distribution and abundance of disease vectors are directly related to climatic conditions and environmental changes. Remote sensing data have been used for monitoring environmental conditions influencing spatial patterns of vector-borne diseases. The aim of this study was to analyze the effect of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and climatic factors (temperature, humidity, wind velocity, and accumulated rainfall) on the distribution and abundance of Anopheles species in northwestern Argentina using Poisson regression analyses. Samples were collected from December, 2001 to December, 2005 at three localities, Aguas Blancas, El Oculto and San Ramón de la Nueva Orán. We collected 11,206 adult Anopheles species, with the major abundance observed at El Oculto (59.11%), followed by Aguas Blancas (22.10%) and San Ramón de la Nueva Orán (18.79%). Anopheles pseudopunctipennis was the most abundant species at El Oculto, Anopheles argyritarsis predominated in Aguas Blancas, and Anopheles strodei in San Ramón de la Nueva Orán. Samples were collected throughout the sampling period, with the highest peaks during the spring seasons. LST and mean temperature appear to be the most important variables determining the distribution patterns and major abundance of An. pseudopunctipennis and An. argyritarsis within malarious areas.

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.

First Report of Chrysomya Megacephala (Diptera: Calliphoridae) in Northwestern Argentina

The Calliphoridae family comprises around150 genera and more than 1000 species distrib-uted world wide (Hennig 1973; Pont 1980; Sh-ewell 1987). Chrysomya Robineau-Desvoidy(Diptera: Calliphoridae) is an especially impor-tant genus because its species are reported asinvaders in South America (Guimaraes et al.1978), and they are involved in the transmis-

New Records of Mosquitoes from Northwestern Argentina

Abstract Eleven mosquito species, namely Aedes hastatus, Ae. fulvus, Coquillettidia albicosta, Cq. juxtamansonia, Culex aliciae, Cx. delpontei, Cx. oedipus, Cx. pedroi, Mansonia flaveola, Uranotaenia leucoptera, and Wyeomyia oblita, are recorded for the first time from northwestern Argentina. In addition, 3 species, Cx. brethesi, Limatus durhami, and Ur. nataliae, are reported for the first time from Salta Province. These records extend the geographical distribution of these 3 species to Salta Province. This study also extends the geographical distributions of Cq. nigricans, Cx. chidesteri, and Ma. humeralis to Jujuy Province and of Ae. meprai, Ae. milleri, Ae. oligopistus, Cx. brethesi, Cx. fernandezi, and Cx. tatoi to Tucumán Province.

Mansonella ozzardi: a neglected New World filarial nematode.

Mansonella ozzardi (Nematoda: Onchocercidae) is an understudied filarial nematode, originally described by Patrick Manson in 1897, that can be transmitted by two families of dipteran vectors, biting midges (most of them members of the genus Culicoides) and black flies (genus Simulium). With a patchy geographic distribution from southern Mexico to northwestern Argentina, human infection with M. ozzardi is highly prevalent in some of the Caribbean islands, along riverine communities in the Amazon Basin, and on both sides of the border between Bolivia and Argentina. There is no clinical entity unequivocally associated with M. ozzardi infection, although fever, arthralgia, headache, cold lower extremities, and itchy cutaneous rashes are occasionally mentioned in case report series. More recently, ocular manifestations (especially keratitis) have been associated with mansonelliasis, opening an important area of investigation. Here, we briefly review the biology, epidemiology, pathogenesis, and clinical aspects of M. ozzardi infection and point to some existing knowledge gaps, aiming to stimulate a research agenda to help filling them.

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.

Longitudinal Study of the Species Composition and Spatio-Temporal Abundance of Anopheles Larvae in a Malaria Risk Area in Argentina

Abstract Species composition and spatio-temporal abundance of Anopheles (Diptera: Culicidae) larvae and their relationship with environmental variables were studied in an endemic malarious area of northwestern Argentina, where Anopheles pseudopunctipennis is the main vector involved in malaria transmission. From Dec 2001 to Dec 2005, we performed monthly samplings of different aquatic larval habitats, such as puddles, irrigation canals, ponds and pools of Mountain Rivers. To determine the relationship among environmental variables and larval abundance, we used Poissons regression analysis. We collected 5,079 larvae of which An. pseudopunctipennis was the most abundant species followed by Anopheles argyritarsis and Anopheles evansae. The density of Anopheles pseudopunctipennis larvae fluctuated between the end of spring until autumn, when malaria cases occur in the area. Concurrently, the larval densities of the other anophelinae species fluctuated throughout these climatic seasons. Poisson regression revealed that an increase of mean minimum temperature produced an increase in the abundance of An. pseudopunctipennis and An. argyritarsis. The mean maximum temperature and the water temperature greatly influenced the abundance of An. pseudopunctipennis, An. evansae and An. strodei. Increases of these temperature variables produced increases in abundance of these species. These factors should be taken into consideration when control measures for immature mosquitoes are implemented to reduce the number of larval habitats and the production of larvae, which may ultimately result in the elimination of malaria in this area.