Cecilia A. Veggiani Aybar

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.

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: 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.

New Records of Culicoides Species (Diptera: Ceratopogonidae) for Bolivia

Culicoides debilipalpis, C insignis, C. lahillei, and C venezuelensis are reported for the first time for Bolivia. The geographical distribution of C. paraensis extends to the Tarija Department.Culicoides debilipalpis, C. insignis, C. lahillei, and C. venezuelensis are reported for the first time for Bolivia. The geographical distribution of C. paraensis extends to the Tarija Department.

Potential Distribution Map of Culicoides insignis (Diptera: Ceratopogonidae), Vector of Bluetongue Virus, in Northwestern Argentina

Abstract Culicoides insignis Lutz is incriminated as a vector of bluetongue virus (BTV) to ruminants in America. In South America, almost all countries have serological evidence of BTV infections, but only four outbreaks of the disease have been reported. Although clinical diseases have never been cited in Argentina, viral activity has been detected in cattle. In this study, we developed a potential distribution map of Culicoides insignis populations in northwestern Argentina using Maximum Entropy Modeling (Maxent). For the analyses, information regarding both data of specimen collections between 2003 and 2013, and climatic and environmental variables was used. Variables selection was based on the ecological relevance in relation to Culicoides spp. biology and distribution in the area. The best Maxent model according to the Jackknife test included 53 C. insignis presence records and precipitation of the warmest quarter, altitude, and precipitation of the wettest month. Accuracy was evaluated by the area under the curve (AUC = 0.97). These results provide an important analytical resource of high potential for both the development of suitable control strategies and the assessment of disease transmission risk in the region.

Latitudinal gradient of biting midges in the genus Culicoides (Diptera: Ceratopogonidae) in Argentina and Bolivia

Abstract We provide the first records of 8 species of biting midges in the genus Culicoides (Diptera: Ceratopogonidae) in a wide latitudinal gradient of the Yungas Ecoregion in Argentina and the Chaco Ecoregion in Bolivia, including a map of their distribution, and an updated checklist of species in the study area. Additional locality records were obtained from published articles and from specimens collected in these and other ecoregions in both countries. Included are the first Argentinean records of Culicoides crescentis Wirth & Blanton and C. pampaensis Spinelli & Wirth from Salta Province; C. caridei Brèthes, C. crescentis, C. guttatus Coquillett, C. insignis Lutz, C. pampaensis, and C. venezuelensis Ortiz & Mirsa from Jujuy Province, and C. saltaensis Spinelli & Wirth and C. pampaensis from Tucumán Province. In addition, the first records of C. brasilianum Forattini, C. crescentis, and C. guttatus are provided from Bolivia.

Survival of the Immature Stages of the Malaria Vectors Anopheles pseudopunctipennis and Anopheles argyritarsis (Diptera: Culicidae) in Northwestern Argentina

Abstract In order to optimally time the application of control measures to reduce populations of malaria vectors, program managers need to know precisely when the vulnerable larval stage will be most abundant at each specific breeding site. Therefore at 4 different breeding sites of the malaria vectors, Anopheles pseudopunctipennis Theobald and Anopheles argyritarsis Robineau-Desvoidy in northwestern Argentina, we recorded the calendar dates during spring and summer when different life stages appeared, and in each of these 2 seasons, we measured the duration of each life stage and the probability that it would transition to the subsequent stage or die. Larval samples were collected during the spring and summer of 2008-2009 at 4 localities in northwestern Argentina. These larvae were reared individually in plastic containers in which the volume of water was kept constant, temperature and photoperiod were controlled, and a standard amount of food was provided each day. The data were analyzed by multistate models, a nonparametric model of survival without covariates, a survival model with covariates, a Cox-type survival model with specific co-variates, and models of reduced rank. We collected 1,643 larvae of which 1,404 reached adulthood. Of these 1,119 were An. pseudopunctipennis, and 285 were An. argyritarsis. Both An. pseudopunctipennis and An. argyritarsis were abundant in autumn (55.3% and 66.7%, respectively). Considerably more individuals transitioned from larvae to pupae than from pupae to adults. The probability of an individual remaining in the larval stage for the first 2 days was close to 100% and then decreased. The transition from the larval stage to death was significant in the summer. The breeding site at Rosario de la Frontera exhibited a particularly significant effect on the transition from the larval stage to death, i.e., greatly increased larval mortality. The results obtained in the present study are substantial contributions to the bionomics of An. pseudopunctipennis and An. argyritarsis. According to our results, mosquito source management programs should be focused on the larval stage during the summer season and principally at Rosario de la Frontera River. These actions could substantially reduce the production of the adult vectors and potentially reduce transmission of malaria in northwestern Argentina.