Dirofilariasis in Argentina: historical review and first report of Dirofilaria immitis in a natural mosquito population

Filarial nematodes in domestic dogs and mosquitoes (Diptera: Culicidae) from semi-rural areas in Central Chile

Climate change, competent vectors, and reservoir animals are the main factors for developing vector-borne zoonotic diseases. These diseases encompass a significant and widespread category of pathogens (e.g., viruses, bacteria, protozoa, and helminths) transmitted by blood-feeding arthropods, including ticks, fleas, lice, triatomines, mosquitoes, sandflies, and blackflies. In Chile, several studies have explored the role of dogs as reservoirs of vector-borne pathogens; however, there is a lack of research investigating the presence of pathogens in arthropods. Specifically, within the order Diptera, limited knowledge exists regarding their roles as carriers of pathogens. This study aimed to examine the presence of zoonotic filarial nematodes in mosquitoes and dogs within a previously unstudied semi-rural area of Central Chile. Two hundred samples of dog blood and seven hundred and twenty-four mosquitoes were collected during 2021-2022 and studied for filarial nematodes by PCR. The prevalence of microfilaremic dogs detected by Knott's test was 7.5%, with Acanthocheilonema reconditum being the only species identified. Aedes (Ochlerotatus) albifasciatus was the most abundant mosquito species collected, and 15 out of 65 pools were positive for filarial nematodes. Among these pools, 13 tested positive for Acanthocheilonema reconditum, and two tested positive for Setaria equina through PCR. Additionally, five Culex pipiens specimens were positive for Acanthocheilonema reconditum. Despite the absence of zoonotic filarial species, these findings underscore the significance of monitoring pathogens in mosquitoes and animal hosts and continued research into the dynamics of vector-borne diseases, particularly in unexplored regions.

The prevalence of canine dirofilariasis in China: a systematic review and meta-analysis

BACKGROUND

Dirofilariasis, the disease caused by Dirofilaria spp., and in particular by Dirofilaria immitis and Dirofilaria repens in canines, occurs frequently in canids and felids, and occasionally in humans, in temperate, sub-tropical and tropical regions globally. Although highly effective, safe and convenient preventive medicines have been available for the treatment of dirofilariasis for the past three decades, the disease remains a major veterinary and public health concern in endemic areas. The insect vectors, host-parasite relationships and interactions of Dirofilaria spp. have received little attention in China, and there is very little information in English regarding the prevalence of dirofilariasis in animals and humans in the country. The aim of this systematic review and meta-analysis is to evaluate the status of canine dirofilariasis in China based on the available literature in English and in Chinese.

METHODS

We systematically searched five databases for epidemiologic studies on the prevalence of canine dirofilariasis in China and finally selected 42 studies eligible for inclusion in the systematic review and meta-analysis. The meta-analysis was performed using the random effects model in the meta package in R v4.2.1.

RESULTS

The random effects model gave a pooled and weighted prevalence of Dirofilaria infection among dogs in China in the past 100 years of 13.8% (2896/51,313, 95% confidence interval 8.2-20.4%) with a high level of heterogeneity (I² =  99.5%).

CONCLUSIONS

Our analyses indicated that the prevalence of canine dirofilariasis in China has gradually declined, but that the range of Dirofilaria spp. has expanded. Older and outdoor dogs presented a higher rate of positive infection. The findings indicated that more attention should be paid to host factors for the effective control and management of this disease.

Parasitism of Dirofilaria incrassata Molin, 1858 in coatis (Nasua nasua)

Populations of the coati, Nasua nasua, like the populations of other wild animals, are regulated by several biotic or abiotic factors. For example, parasites act as a biotic factor affecting the dynamics and density of coati populations. The parasitic nematodes of coatis include Dirofilaria species, such as Dirofilaria immitis, Dirofilaria repens, and Dirofilaria incrassata. Considering that there are few records on parasitism by D. incrassata, including information on the life cycle or location in the host body, this study aimed to investigate the infection of N. nasua by D. incrassata in midwestern Brazil. Thus, two coatis (males and adults) from the Cerrado of Goiás, which died (cause unknown) at the Wild Animal Screening Center/IBAMA in the municipality of Goiânia, Goiás, Midwestern of Brazil, were dissected and all helminths found were collected, identified following specific keys and quantified. A total of 85 specimens of D. incrassata were collected, with a mean parasitic intensity of 42.5 and a parasitic amplitude ranging from 40 to 45, measuring 41-93 mm in length and 0.23-0.45 mm in width. All helminths were adults and were distributed in the superficial and deep fascia (at different levels) from the neck to the hind limb. Most helminths were tangled, with some encased in a connective tissue film. Most reported human heartworm cases refer to subcutaneous or ocular heartworm infection, mainly caused by D. repens, although other species of heartworm may be associated. D. incrassata was not reported as zoonotic agent, diferently of other Dirofilaria species associated with wild animals and with zoonotic potential in the Americas. This study reiterates N. nasua as the definitive host for D. incrassata and the subcutaneous tissue as the site of choice for this helminth in the adult form. In addition, it reports new body regions where the parasite occurs. This study is the first to document the occurrence of D. incrassata infestation in the State of Goiás, Brazil.

A case of natural infection with Dirofilaria immitis in a coati (Nasua narica) from Mexico

This paper aims to describe the natural infection with Dirofilaria immitis in Nasua narica (white-nosed coati) from Yucatán, Mexico. Two carcasses of N. narica were collected on a highway that crosses through a dense forest with patches used for agriculture and livestock activities. We performed necropsies, and two female adult nematode parasites from the heart of one specimen were collected and preserved for their molecular identification using a conventional PCR directed at a fragment of the small subunit (18S) ribosomal RNA (18S-rRNA) gene. Bioinformatic analysis showed a similarity of 99 % with three sequences from D. immitis (two from Japan). Additionally, we performed a phylogenetic tree with the recovered sequence. All these analyses showed that D. immitis is present in N. narica from Mexico. The transmission of D. immitis toward populations of Nasua sp. may be due to indirect and accidental contact with domestic dogs or wild canids that share the same environment.

The Presence of Dirofilaria immitis in Domestic Dogs on San Cristobal Island, Galapagos

This study's concept was outlined around the principle of conservation medicine in a biodiversity hotspot from the Neotropical realm: the Galapagos Islands. The wildlife balance has been modified by multi-host parasites introduced with some domestic animals (dogs and cats). The endemic and endangered species, the Galapagos sea lion (GSL, Zalophus wollebaeki), has been exposed to pathogens of canine and feline origin that could become a significant conservation problem for this species. One of these potential cases is the filarial heartworm infection, Dirofilaria immitis, which has been reported on other pinnipeds, with fatalities and clinical symptoms. Therefore, this study evaluated the presence of the microfilaria of D. immitis in dogs from Puerto Baquerizo Moreno, San Cristobal Island, where the largest rookery of GSLs lives and where the proximity to domestic dogs is the most intimate compared to other rookeries of the archipelago. Between July and September 2021, 587 blood samples were collected from owned dogs of Puerto Baquerizo Moreno. Overall, 10 dogs (1.7%) were positive for the presence of the microfilaria of D. immitis with a confidence interval of 0.7%-2.8%. No other filarial species were identified. Significant differences in prevalence between different dog categories were observed only for the age (p = 0.001). This study represents the first report of D. immitis, the agent of canine heartworm disease, in dogs from San Cristobal Island. Hence, the presence of the microfilaria of D. immitis in the blood of dogs could increase the risk of infection to which the GSL is exposed in the region.

Differential diagnosis of Dirofilaria immitis nematodes (Nematoda, Onchocercidae)

Heartworm disease is a widespread anthropozoonotic disease of carnivorous animals, as well as humans. It is caused by nematodes belonging to the suborder Filariata, family Onchocercidae, genus Dirofilaria. There are about 26 species of heartworms in nature, the most common and pathogenic species in dogs and cats in most countries is Dirofilaria immitis Leidy, 1856. Mature helminths parasitize in the right ventricle and pulmonary arteries, large veins of animals and cause heart and vascular disorders, and death. Therefore, the aim of the study was to investigate the features of morphological and metric structure of adult nematodes of D. immitis isolated from the heart of dogs. Morphological studies have shown that in males the most characteristic differential features are the presence of two unequal spicules, specifically positioned relative to each other, as well as well-defined preanal and less pronounced adanal and postanal papillae. In female heartworms, the characteristic morphological features are the shape and location of the vulva. There is a difference in the structure of the esophagus in males and females. In females, the anterior and posterior parts of the esophagus are well expressed, with enlargements, in males these divisions are not pronounced. To increase the efficiency of species identification of D. immitis nematodes, it is proposed to use metric parameters that characterize the overall body size, body and width of esophagus in different areas, length of esophagus, and the location of the nerve ring. In males, 11 indicators are also suggested that characterize the size of the spicules and the location of the cloaca. In females, seven additional parameters are pointed out that characterize the location of the vulva, anus and body width in these areas. The obtained data expand the already existing data on the peculiarities of the morphological structure of parasitic nematodes of the species D. immitis and their identification.

Prevalence of Dirofilaria immitis in mosquitoes (Diptera) - systematic review and meta-analysis

Knowledge of the vectors of dirofilariasis in the world beside the treatment of infected dog is crucial to establish mosquito vector-based control programs. The current systematic review and meta-analysis were conducted on published studies, documenting the prevalence of Dirofilaria immitis infected/infective mosquitoes from field surveys and laboratory experiments under controlled conditions. Articles up through 2019 from Scopus, PubMed, Embase, Web of Science, Google Scholar were screened systematically. The overall prevalence of D. immitis infected/infective mosquitoes was estimated using a random effect model. Meta-regression was used to identify factors related to high dirofilariasis prevalence in the vectors. In these studies, the detection method was not identified as a heterogeneity and the overall prevalence in both subgroups had overlap (7.9-34.9 and 1.5-48.5). The overall prevalence of infective stage was 2.6 (95% CI: 0.97-4.77 per 1,000) and 84.7 per 1000 (95% CI: 20.5-183.8 per 1,000) for the field survey/laboratory experiment, respectively. The higher overall prevalence of D. immitis infected/infective mosquitoes were reported across studies in which take place in Eastern Mediterranean Region office (EMRO), longitude: 80 to 110, latitude: 20 to 40, annual rainfall: 250 to 1000, sea level: 26 to 100 and <1,000, humidity: 66 to 70, during 2000 to 2005 by dissection methods. Our review determined that mosquito species within the genus Anopheles and to a less extent Culex were the main vectors of dirofilariasis.

Susceptibility of the floodwater mosquito Aedes albifasciatus from eggs of different dormancy times to the nematode parasite Strelkovimermis spiculatus

This study aimed to evaluate the effects of egg dormancy times on susceptibility of larvae of the floodwater mosquito Aedes albifasciatus (Diptera: Culicidae) to parasitism by their natural enemy Strelkovimermis spiculatus (Nematoda: Mermithidae) and on their life history traits. Aedes albifasciatus eggs stored for 2, 4, 6, 8 and 10 months were hatched, and the larvae either exposed to S. spiculatus (treatment group) or not exposed (control group). Egg dormancy time had a negative effect on the retention of parasites, but no effect on the prevalence and intensity of parasitism or the melanization of nematodes. The survival to adulthood of control individuals decreased as dormancy time increased, whereas that of exposed individuals that remained uninfected was constant and low. A trend towards increasing development times with longer dormancy times was detected in the control group, but not in the exposed noninfected group. The results suggest nonconsumptive effects of parasites in exposed but not infected larvae from eggs with short dormancy times. In contrast, the relatively low fitness of larvae from eggs with long dormancy times regardless of their contact with the nematodes may be the result of the nutritional deprivation during the egg stage.

Overview on Dirofilaria immitis in the Americas, with notes on other filarial worms infecting dogs

Canine dirofilariosis in the Americas is primarily caused by Dirofilaria immitis, a mosquito-borne filarial worm infecting dogs, which may also infect and cause disease in other mammalian hosts, including humans. Morphological and molecular evidence gathered in the past decades suggest that other Dirofilaria spp. may infect dogs in the American continent, though the actual taxonomic identity of them still needs to be elucidated. In addition, filarial worms belonging to distinct genera have also been reported in dogs in this part of the world, including Acanthocheilonema reconditum, Cercopithifilaria bainae, and Onchocerca lupi. Among these, O. lupi is a species of major clinical significance, which has been reported not only in dogs, but also in cats and humans in North America. The present article provides a current overview on canine dirofilariosis in the Americas, with notes on other filarial worms infecting dogs. It also provides some insights into outstanding research questions that should be responded to fill some of the several knowledge gaps related to this group of parasites in this continent.

Mosquito (Diptera: Culicidae) larval ecology in natural habitats in the cold temperate Patagonia region of Argentina

BACKGROUND

Knowledge of immature habitats is an important focus for investigations of mosquito community ecology, and may improve our understanding of how environmental variables increase risk of mosquito-borne diseases by influencing the distributions and abundances of species. In Patagonia region, where climatic and ecological factors could be only borderline suitable for mosquito development, relatively little is known about larval ecology. The present study focuses on associations of environmental conditions in natural aquatic habitats with abundances of mosquito species that have colonized such habitats in Patagonia.

METHODS

We described the mosquito community composition within 26 natural temporary pools, and assessed the general relationships between environmental variables (pH, water temperature, conductivity, salinity, dissolved oxygen, aquatic plant cover and main nutrients) and larval abundances using redundancy analysis (RDA). Additionally, we compiled monthly climate data and vegetation indices for each larval habitat, and estimated the probability of presence for two of the most abundant species, describing through generalized linear models (GLM) the environmental, climatic and landscape variables-probability of occurrence relationships.

RESULTS

Seven species belonging to the genera Culex and Aedes were identified, with Culex apicinus, Cx. acharistus and Aedes albifasciatus being the most abundant. Mean larval densities were low (6.8 ± 2.8 larvae/dip), and the highest species richness and larval densities were recorded in northern and central areas. Aedes albifasciatus, a species of sanitary importance, was widely distributed, being the only one collected south of the 45th parallel of S latitude. RDA indicated that aquatic conductivity, pH, water depth, dissolved oxygen, ammonia and soluble reactive phosphorous accounted for the main part of the variation in the species composition. According to GLMs, wind speed was the variable that best described the presence of Ae. albifasciatus, and the probability of finding this species was positively associated with high wind speed values. On the other hand, the EVI vegetation index was the only variable included in the Cx. apicinus model, whereby there was a great probability of presence in arid areas with lower EVI values.

CONCLUSIONS

Our results enhance our knowledge of larval habitat ecology under the extreme environmental conditions of Patagonia and will guide future efforts to understand how multiple effects can affect mosquito ecology and public health at higher latitudes.

A review on the occurrence of companion vector-borne diseases in pet animals in Latin America

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

New record and extended geographical distribution of Aedes fluviatilis (Lutz, 1904) in Ceará, northeastern Brazil

INTRODUCTION

Aedes fluviatilis(Lutz, 1904) is considered a potential vector of yellow fever and dengue viruses and is naturally infected by Wolbachia.

METHODS

In March 2018, during a field activity in the municipality of Saboeiro, 163 mosquito larvae were collected in a dammed area of the Jaguaribe River.

RESULTS

Of the larvae collected, 143 (87.7%) were identified asAe. fluviatilis.

CONCLUSIONS

We report the first documentation of Ae. fluviatilis in the municipality of Saboeiro, northeastern Brazil. It is important to conduct additional entomological surveys to characterize the local Culicidae fauna. Ignoring the presence and dispersion of this vector could be a public health risk.

Wing morphometrics of Aedes (Ochlerotatus) albifasciatus (Macquart, 1838) (Diptera: Culicidae) from different climatic regions of Argentina

BACKGROUND

Gene flow restrictions between populations of Aedes albifasciatus, the vector of Western equine encephalitis and Dirophilaria immitis, have been described in the central region of Argentina. Genetic and eco-physiological variations usually result in local forms reflecting the climatic regions. Mosquito wings and their different parts have ecological functions in flight and communication. Therefore, wing shape could be considered an aspect of sexual dimorphism, and its eco-physiological responses can be expressed as morphological changes induced by the environment.

METHODS

To compare the geographical and sexual variations with respect to wing shape and size in two Ae. albifasciatus populations from contrasting climates of Argentina (temperate: Buenos Aires, and the arid steppe of Patagonia: Sarmiento), the wings of adults reared in thermal trays at different constant temperatures (10-29 °C) were analyzed.

RESULTS

The wing size of Ae. albifasciatus showed inverse linear relationships with the rearing thermal condition and higher slope for Buenos Aires. In the cool range (10-17 °C), geographical size variations responded to the converse Bergmann's rule, where Buenos Aires individuals were larger than those from Sarmiento. Sexual shape dimorphism occurred in both populations while geographical variation in shape was observed in both sexes.

CONCLUSIONS

Buenos Aires individuals showed greater response sensitivity with respect to the size-temperature relation than those from Sarmiento. The converse Bergmann's rule in size variation could be due to a higher development rate in Sarmiento to produce more cohorts in the limited favorable season. The shape could be more relevant with respect to the size in the study of population structures due to the size being more liable to vary due to changes in the environment. The geographical variations with respect to morphology could be favored by the isolation between populations and adaptations to the environmental conditions. Our results demonstrate that the shape and size of wing provide useful phenotypic information for studies related to sexual and environmental adaptations.

Heterogeneous distribution of Dirofilaria immitis in dogs in St. Kitts, West Indies, 2014-2015

In the Caribbean region, Dirofilaria immitis (heartworm) has been detected on almost all of the islands. While it is assumed to be endemic throughout the region, there is a lack of baseline data from the Leeward Islands (north-east of the Caribbean region). The objective of this study was to estimate the prevalence and the spatial distribution of heartworm disease in dogs on St. Kitts, a small 174km² island which is part of the Leeward Islands. A cross-sectional study was conducted in 2014 with 100 dogs tested using a commercial antigen test. Dogs were from all regions of the island except the southeastern region, which differs socio-economically from the rest of the island. Heartworm was not detected in these 100 dogs. To complete the survey, in 2015, fifteen dogs from the southeast region were tested, eight of which were positive for heartworm. Prevalence was estimated at 7.0% (95% confidence interval: 4.6-11.6). Data from two other sources were added to complete the report: data from dogs enrolled in a free spay and neuter program and tested against heartworm (164 dogs with 3 positive for heartworm), and the data from positive dogs diagnosed at the Ross University Veterinary Clinic in 2014 and 2015 (3 dogs). Most of the heartworm positive dogs (10/14) lived in a delimited area in the southeast of the island. These results indicate an overall low prevalence of Dirofilaria immitis in St. Kitts, lower than that observed in the other Caribbean islands. Heterogeneity in the spatial distribution of the parasite was observed, with the majority of cases residing in the southeast of the island. Previous spatial models focused on the spread of the parasite over large geographical areas and long distances, but not within a restricted area. Our results indicate the presence of local factors which may have limited spread of the disease over short distances. Further studies are needed to understand this markedly heterogeneous distribution.

The Complexity of Zoonotic Filariasis Episystem and Its Consequences: A Multidisciplinary View

Vector-borne transmitted helminthic zoonosis affects the health and economy of both developing and developed countries. The concept of episystem includes the set of biological, environmental, and epidemiological elements of these diseases in defined geographic and temporal scales. Dirofilariasis caused by different species of the genus Dirofilaria is a disease affecting domestic and wild canines and felines and man, transmitted by different species of culicid mosquitoes. This complexity is increased because Dirofilaria species harbor intracellular symbiont Wolbachia bacteriae, which play a key role in the embryogenesis and development of dirofilariae and in the inflammatory pathology of the disease. In addition, the vector transmission makes the dirofilariasis susceptible to the influence of the climate and its variations. The present review addresses the analysis of dirofilariasis from the point of view of the episystem, analyzing the complex network of interactions established between biological components, climate, and factors related to human activity, as well as the different problems they pose. The progress of knowledge on human and animal dirofilariasis is largely due to the multidisciplinary approach. Nevertheless, different aspects of the disease need to continue being investigated and cooperation between countries and specialists involved should be intensified.

Detection of Mycoplasma haemocanis, Mycoplasma haematoparvum, Mycoplasma suis and other vector-borne pathogens in dogs from Córdoba and Santa Fé, Argentina

Background

In Argentina, only very few reports are available for canine tick-borne diseases where most are related to parasitic diseases. The objective of this survey was to investigate the prevalence of tick-borne pathogens in 70 dogs from Santa Fé and Córdoba, Argentina.

Methods

Microscopic blood smear examination as well as polymerase chain reaction (PCR) amplification using species-specific markers of Anaplasma, Babesia, Bartonella, Borrelia, Ehrlichia, Francisella, Mycoplasma (hemotropic group) and Rickettsia, followed by DNA sequencing were used to establish the prevalence of each infecting pathogen.

Results

Blood smear analysis showed 81% (57/70) prevalence of structures morphologically compatible with hemotropic mycoplasmas. No structures resembling either piroplasms or Anaplasma/Ehrlichia were detected. Hemotropic mycoplasma species (Mycoplasma haematoparvum, Mycoplasma haemocanis and Mycoplasma suis) were the most prevalent pathogens detected with an overall prevalence of 77.1%. Anaplasma platys was detected and identified in 11 of the 70 dogs (15.7%), meanwhile two Bartonella spp. (B. clarridgeiae and an uncharacterized Bartonella sp.) and Babesia vogeli were detected at 3 and 7% prevalence, respectively.

Conclusions

The work presented here describes a high molecular prevalence for hemotropic mycoplasma species in each of the five locations selected. Three Mycoplasma spp., including Mycoplasma suis, reported for the first time in dogs have been identified by DNA amplification and sequencing. This study highlights the risk that these bacterial pathogens represent for companion animals and, due to their potential zoonotic nature, also for people.

Population Genetic Structure of Aedes fluviatilis (Diptera: Culicidae)

Although Aedes fluviatilis is an anthropophilic mosquito found abundantly in urban environments, its biology, epidemiological potential and genetic characteristics are poorly understood. Climate change and urbanization processes that result in environmental modifications benefit certain anthropophilic mosquito species such as Ae. fluviatilis, greatly increasing their abundance in urban areas. To gain a better understanding of whether urbanization processes modulate the genetic structure of this species in the city of São Paulo, we used eight microsatellite loci to genetically characterize Ae. fluviatilis populations collected in nine urban parks in the city of São Paulo. Our results show that there is high gene flow among the populations of this species, heterozygosity deficiency and low genetic structure and that the species may have undergone a recent population expansion. There are two main hypotheses to explain these findings: (i) Ae. fluviatilis populations have undergone a population expansion as a result of urbanization; and (ii) as urbanization of the city of São Paulo occurred recently and was quite intense, the structuring of these populations cannot be observed yet, apart from in the populations of Ibirapuera and Piqueri parks, where the first signs of structuring have appeared. We believe that the expansion found in Ae. fluviatilis populations is probably correlated with the unplanned urbanization of the city of São Paulo, which transformed green areas into urbanized areas, as well as the increasing population density in the city.

Co-Infection and Wild Animal Health: Effects of Trypanosomatids and Gastrointestinal Parasites on Coatis of the Brazilian Pantanal

Wild animals are infected by diverse parasites, but how they influence host health is poorly understood. We examined the relationship of trypanosomatids and gastrointestinal parasites with health of wild brown-nosed coatis (Nasua nasua) from the Brazilian Pantanal. We used coati body condition and hematological parameters as response variables in linear models that were compared using an information theoretic approach. Predictors were high/low parasitemias by Trypanosoma cruzi and T. evansi, and indices representing the abundance of distinct groups of gastrointestinal parasites. We also analyzed how host health changed with host sex and reproductive seasonality. Hemoparasites was best related to coati body condition and hematological indices, whereas abundance of gastrointestinal parasites was relatively less associated with coati health. Additionally, some associations were best predicted by models that incorporated reproductive seasonality and host sex. Overall, we observed a lower health condition during the breeding season, when coatis are under reproductive stress and may be less able to handle infection. In addition, females seem to handle infection better than males. Body condition was lower in coatis with high parasitemias of T. evansi, especially during the reproductive season. Total red blood cell counts, packed cell volume, platelets and eosinophils were also lower in animals with high T. evansi parasitemias. Total white blood cell counts and mature neutrophils were lower in animals with high parasitemias for both Trypanosoma species, with neutrophils decreasing mainly during the reproductive season. Overall, decreases in hematological parameters of females with T. evansi high parasitemias were less evident. For T. cruzi, monocytes decreased in individuals with high parasitemias. High abundances of microfilariae in the bloodstream, and cestode eggs and coccidian oocysts in feces were also associated with coati blood parameters. This study shows the potential value of examining hematological parameters as an approach to better understand the ecological relevance of parasite-host interactions.

Modeling the extrinsic incubation of Dirofilaria immitis in South America based on monthly and continuous climatic data

The spread and recrudescence of dirofilariosis across several regions, either caused by Dirofilaria immitis or D. repens, responds to many factors. Building upon the temperature model by Slocombe et al. (1989), a number of studies have been performed to generate predictive models for dirofilariosis. These studies have demonstrated the length of transmission periods and the number of Dirofilaria generations supported throughout several regions of the world (either at large or at small-scale). The usual procedure have proved to be extremely time consuming, as it appears impractical when assessing potential transmission at large scale, such as at a country or large-scale level. Due to the increasing need to suggest standardized surveillance protocols and apply adequate preventive measures at national and regional levels, a model for calculation of Dirofilaria HDUs based on monthly data was adapted for large-scale regional use. The models proposed are based on both point data (meteorological stations) and interpolated climate data layers (WorldClim). Three different models (daily and monthly models based on point data, and monthly model based on continuous data) were developed and compared statistically. When compared with the results from the classical daily model, the monthly models proposed accurately predicted the locations were extrinsic incubation was possible. These models proved to be adequate for the regional analysis of the extrinsic incubation of D. immitis and, hence, the relative risk of transmission in South America. Further, these models confirm that favorable temperatures for heartworm transmission in South America are present in most of the countries. D. immitis extrinsic incubation follows a seasonal pattern in Argentina, Chile, Uruguay, eastern Paraguay and southeastern Brazil; while in northern half of South America (less than 25° S) transmission may occur year-round. Moreover, high risk areas suitable for dirofilariasis transmission are not geographically constant throughout the year. The validation procedures indicate that the predicted HDU and HG maps are good predictors of dirofilariosis potential distribution, but estimating dirofilariosis prevalences based on them might not be completely accurate. The resulting distribution and seasonal maps would be useful for heartworm prevention by chemoprophylaxis in different regions known to be endemic for canine dirofilariasis. The information here provided can be an important tool in veterinary public health, as well as a guide for future research.

Aedes aegypti from temperate regions of South America are highly competent to transmit dengue virus

BACKGROUND

Aedes aegypti is extensively spread throughout South America where it has been responsible for large dengue epidemics during the last decades. Intriguingly, dengue transmission has not been reported in Uruguay and is essentially prevalent in subtropical northern Argentina which borders Uruguay.

METHODS

We assessed vector competence for dengue virus (DENV) of Ae. aegypti populations collected in subtropical Argentina (Corrientes) as well as temperate Uruguay (Salto) and Argentina (Buenos Aires) in 2012 using experimental oral infections with DENV-2. Mosquitoes were incubated at 28 °C and examined at 14 and 21 days p.i. to access viral dissemination and transmission. Batches of the Buenos Aires mosquitoes were also incubated at 15 °C and 20 °C.

RESULTS

Although mosquitoes from temperate Uruguay and Argentina were competent to transmit DENV, those from subtropical Argentina were more susceptible, displaying the highest virus titters in the head and presenting the highest dissemination of infection and transmission efficiency rates when incubated at 28 °C. Interestingly, infectious viral particles could be detected in saliva of mosquitoes from Buenos Aires exposed to 15 °C and 20 °C.

CONCLUSIONS

There is a potential risk of establishing DENV transmission in Uruguay and for the spread of dengue outbreaks to other parts of subtropical and temperate Argentina, notably during spring and summer periods.

Imperviousness as a predictor for infestation levels of container-breeding mosquitoes in a focus of dengue and Saint Louis encephalitis in Argentina

Dengue and Saint Louis encephalitis virus are among the most important emerging viruses transmitted by mosquitoes at the global scale, and from 2009 onward both diseases have reached temperate Argentina. To test whether the urbanization level can be used as a predictor for the infestation levels of container-breeding mosquito vectors, we searched for Aedes aegypti and Culex pipiens in 8400 water-filled containers from 14 cemeteries of Buenos Aires Province and we used generalized linear models to relate positive containers with the impervious area quantified inside (internal PIA) and outside (external PIA) cemeteries. The best model for Ae. aegypti explained 91% of the variability and included the season, the internal PIA and the external PIA at 1km as a quadratic function, showing a parabolic response peaking in ∼75%. Regarding the infestation levels of Cx. pipiens, the final model explained 75% of the variability and included only the season. In view of these results, the percentage of impervious area efficiently predicted the infestation levels of Ae. aegypti but not of Cx. pipiens. Considering the worldwide relevance of the former in dengue transmission, the simple quantification of imperviousness proposed herein provides a helpful basis for vector surveillance and control in urbanized areas.

Dirofilariosis in the Americas: a more virulent Dirofilaria immitis?

Dirofilarioses are widespread diseases caused by filarioid nematodes (superfamily Filarioidea) of the genus Dirofilaria, which are transmitted by a plethora of mosquito species. The principal agent of canine dirofilariosis in the Americas is Dirofilaria immitis, which may also occasionally infest humans, resulting in pulmonary nodules that may be confounded with malignant lung tumours. Because human cases of dirofilariosis by D. immitis are relatively frequent in the Americas and rare in Europe and other eastern countries, where Dirofilaria repens is the main causative agent, the existence of a more virulent strain of D. immitis in the Americas has been speculated. Recently, a case of human ocular infestation by Dirofilaria sp. was diagnosed in Pará State, northern Brazil, where canine heartworm dirofilariosis is endemic. The nematode was shown to be morphologically and phylogenetically related to D. immitis but it was genetically distinct from reference sequences, including those of D. immitis infesting dogs in the same geographical area. This finding raised questions regarding the aetiology of human dirofilariosis in the Americas, since information on the genetic makeup of filarioids infesting dogs and humans is meagre. Further studies would be needed to better characterize filarioids infesting dogs, wild animals, and humans in the Americas and to assess the existence of a more virulent D. immitis strain in this continent. Finally, the competence of different culicid species/strains from Europe and the Americas as vectors of Dirofilaria species should be investigated. Such studies would help us to understand possible variations in transmission patterns and even to predict possible scenarios that may emerge in the future, with the introduction of non-endemic Dirofilaria species/strains in free areas through importation of infested animals, vectors, or both.

Culex pipiens affected by joint infection of a mosquito iridescent virus and Strelkovimermis spiculatus

Dual infections with a mosquito iridescent virus (MIV) and the mermithid nematode, Strelkovimermis spiculatus were recorded in natural Culex pipiens populations around La Plata city, Argentina. S. spiculatus was detected in 82% of samples that were positive for MIV infection. Dissected larvae of Cx. pipiens with patent MIV infection presented 42% infection with S. spiculatus. Larvae of Cx. pipiens exposed to MIV and S. spiculatus under laboratory conditions produced a high joint infection rate (82.5%) while no infection was recorded on larvae exposed to virus suspension only. Field and laboratory results suggest a strong association between S. spiculatus and MIV in natural populations of Cx. pipiens, in which S. spiculatus could be a mode of entry for the virus into the mosquito hemocele.

North American wetlands and mosquito control

Wetlands are valuable habitats that provide important social, economic, and ecological services such as flood control, water quality improvement, carbon sequestration, pollutant removal, and primary/secondary production export to terrestrial and aquatic food chains. There is disagreement about the need for mosquito control in wetlands and about the techniques utilized for mosquito abatement and their impacts upon wetlands ecosystems. Mosquito control in wetlands is a complex issue influenced by numerous factors, including many hard to quantify elements such as human perceptions, cultural predispositions, and political climate. In spite of considerable progress during the last decades, habitat protection and environmentally sound habitat management still remain inextricably tied to politics and economics. Furthermore, the connections are often complex, and occur at several levels, ranging from local businesses and politicians, to national governments and multinational institutions. Education is the key to lasting wetlands conservation. Integrated mosquito abatement strategies incorporate many approaches and practicable options, as described herein, and need to be well-defined, effective, and ecologically and economically sound for the wetland type and for the mosquito species of concern. The approach will certainly differ in response to disease outbreaks caused by mosquito-vectored pathogens versus quality of life issues caused by nuisance-biting mosquitoes. In this contribution, we provide an overview of the ecological setting and context for mosquito control in wetlands, present pertinent information on wetlands mosquitoes, review the mosquito abatement options available for current wetlands managers and mosquito control professionals, and outline some necessary considerations when devising mosquito control strategies. Although the emphasis is on North American wetlands, most of the material is applicable to wetlands everywhere.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Heartworm Disease (Dirofilaria immitis) and Their Vectors in Europe - New Distribution Trends

Cardiopulmonary dirofilariasis is a cosmopolitan disease caused by Dirofilaria immitis, which affects mainly canids and felids. Moreover, it causes zoonotic infections, producing pulmonary dirofilariasis in humans. Heartworm disease is a vector-borne transmitted disease, thus transmission depends on the presence of competent mosquito species, which is directly related to favorable climate conditions for its development and survival. Cardiopulmonary dirofilariasis is mainly located in countries with temperate and tropical climates. Europe is one of the continents where animal dirofilariasis has been studied more extensively. In this article we review the current prevalence of canine and feline cardiopulmonary dirofilariasis in the European continent, the transmission vectors, the current changes in the distribution and the possible causes, though the analysis of the epidemiological studies carried out until 2001 and between 2002 and 2011. The highest prevalences have been observed in the southern European countries, which are considered historically endemic/hyperendemic countries. Studies carried out in the last 10 years suggest an expansion of cardiopulmonary dirofilariasis in dogs toward central and northern Europe. Several factors can exert an influence on the spreading of the disease, such as movement of infected animals, the introduction of new species of mosquitoes able to act as vectors, the climate change caused by the global warming, and development of human activity in new areas. Veterinary controls to prevent the spreading of this disease, programs of control of vectors, and adequate protocols of prevention of dirofilariasis in the susceptible species should be carried out.

An update of mosquitoes of Argentine Patagonia with new distribution records

The objective of this study was to update mosquito species distribution in Argentine Patagonia based on new field collections and to examine the material deposited in the La Plata Museum. Culex coronator, Cx. brethesi, and Cx. castroi represented new records for the region, increasing mosquito fauna of Patagonia to 15 species. The expansion of the geographic distribution of Cx. apicinus, Cx. articularis, and Cx. eduardoi at the province level was also provided. Current knowledge about mosquito fauna of Patagonia is restricted mainly to geographic distribution records. Further studies on the bionomic of mosquito species in Patagonian conditions are needed.

Survey of Canine Dirofilaria immitis Infection in New Caledonia

Canine dirofilariosis is a frequent parasitic disease in New-Caledonia. A survey of canine heartworm (Dirofilaria immitis) infection among dogs from the cities of Tontouta, Nandaï and Nouméa, was performed in March 2009 using two antigen test kits; the microwell ELISA test: DiroCHE (Synbiotics Europe) and the Rapid Immuno Migration (RIM) test: WITNESS DIROFILARIA (Synbiotics Europe). Blood samples were collected from 64 dogs: 49 strays and 15 military working dogs. The military dogs received a permanent chemoprophylaxis (moxidectin). In 11 stray dogs, both tests were positive (22.4%). All the military dogs were negative, showing efficiency of chemoprophaxis. Results were discrepant in 6 dogs, negative with one test and doubtful with the other. Antigen heartworm test kits are available and reliable diagnostic tools. They are useful to evaluate the efficiency of chemoprophylaxis and to detect infected animals in order to treat them and to prevent the spreading of the disease.

PCR detection of Dirofilaria immitis in Aedes aegypti and Culex pipiens from urban temperate Argentina

Dirofilariasis, a mosquito-borne disease of dogs caused by the nematode Dirofilaria immitis (Leidy; Spirurida: Onchocercidae), has now become a growing zoonotic concern. Based on direct microscopical observation, Aedes aegypti (L.) and Culex pipiens L. (Diptera: Culicidae) have been previously incriminated as potential vectors of D. immitis in urban temperate Argentina. In this study, an effort was made to provide evidence for this assumption by screening of mosquitoes for D. immitis infection using a polymerase chain reaction (PCR) assay. PCR primers were developed to specifically amplify the D. immitis-16S rRNA gene and to reliably detect 100th of the genomic equivalent (10 pg) of the infective third-stage larvae in mosquito pools of up to 30 individuals. Collection of mosquitoes was performed between September 2007 and April 2008 in premises known to be inhabited by D. immitis-infected dogs in Greater Buenos Aires. The final collection comprised 453 specimens belonging to 11 mosquito species of the genera Aedes, Culex, Ochlerotatus, and Psorophora. PCR assays were performed on 82 pools (n ≤ 20) of heads and abdomens separately, as this allows differentiating infective and non-infective stages of the parasite, respectively. Identification of the non-infective stage of D. immitis in A. aegypti and C. pipiens provided additional strong support of transmission of the parasite by these species. To our knowledge, this was the first PCR screening for D. immitis-infected mosquitoes in South America.

Prevalence of Dirofilaria immitis in dogs from Hatay province, Turkey

The present study was conducted to determine the prevalence of canine dirofilariosis in Hatay province, south of Turkey. A total of 269 blood samples were collected from owned dogs in this multi-centre survey between March and July 2006. Blood samples were examined by modified Knott and enzyme-linked immunosorbent assay (ELISA) techniques to detect circulating microfilariae and antigens of Dirofilaria immitis, respectively. Seventy out of 269 dogs (26.0%) were positive for D. immitis. However, 61.4% of positive dogs had occult infection. The prevalence of canine dirofilariosis was heterogeneous in Hatay province, with higher values in shoreline (33.0%) and riverside (30.9%) areas followed by the lowland (25.5%) or mountainous (15.2%) areas. No statistically significant differences were observed in relation to sex (females, 33.3%; males, 24.4%, P>0.05). When evaluating the prevalence of D. immitis by age, the highest prevalence was observed in dogs older than 4 years of age. Large breeds (29.6%) and the dogs living outdoors (30.2%) showed a higher prevalence in comparison to small breeds (21.4%) and the dogs living indoors (10.5%), respectively. In conclusion, according to the results of this study canine dirofilariosis had a high prevalence in Hatay province. Therefore, prophylaxis against heartworm is advisable to decrease the incidence of canine dirofilariosis.

Loop-mediated isothermal amplification applied to filarial parasites detection in the mosquito vectors: Dirofilaria immitis as a study model

Background

Despite recent advances in our understanding of the basic biology behind transmission of zoonotic infectious diseases harbored by arthropod vectors these diseases remain threatening public health concerns. For effective control of vector and treatment, precise sampling indicating the prevalence of such diseases is essential. With an aim to develop a quick and simple method to survey zoonotic pathogen-transmitting vectors, LAMP (loop-mediated isothermal amplification) was applied to the detection of filarial parasites using a filarial parasite-transmitting experimental model that included one of the mosquito vectors, Aedes aegypti, and the canine heartworm, Dirofilaria immitis.

Results

LAMP reactions amplifying the cytochrome oxidase subunit I gene demonstrated high sensitivity when a single purified D. immitis microfilaria was detected. Importantly, the robustness of the LAMP reaction was revealed upon identification of an infected mosquito carrying just a single parasite, a level easily overlooked using conventional microscopic analysis. Furthermore, successful detection of D. immitis in wild-caught mosquitoes demonstrated its applicability to field surveys.

Conclusion

Due to its simplicity, sensitivity, and reliability, LAMP is suggested as an appropriate diagnostic method for routine diagnosis of mosquito vectors carrying filarial parasites. This method can be applied to the survey of not only canine filariasis but also lymphatic filariasis, another major public health problem. Therefore, this method offers great promise as a useful diagnostic method for filarial parasite detection in endemic filariasis regions.

The effect of shade on the container index and pupal productivity of the mosquitoes Aedes aegypti and Culex pipiens breeding in artificial containers

The aim of this study was to assess whether certain attributes of larval breeding sites are correlated with pupal productivity (i.e. numbers of pupae collected per sampling period), so that these could be used as the focus for control measures to enhance control efficiency. Therefore, the objectives were to identify the months of highest pupal productivity of Aedes aegypti (L.) and Culex pipiens L. (Diptera: Culicidae) in an urban temperate cemetery in Argentina where artificial containers of < 6 L (flower vases) were the predominant breeding habitats, to compare various measures of the productivity of sunlit and shaded containers and to determine whether the composition of the containers affected pupal productivity. Over a period of 9 months, 200 randomly chosen water-filled containers (100 sunlit and 100 shaded), out of approximately 3738 containers present (approximately 54% in shade), were examined each month within a cemetery (5 ha) in Buenos Aires (October 2006 to June 2007). In total, 3440 immatures of Cx pipiens and 1974 of Ae. aegypti were collected. The larvae : pupae ratio was 10 times greater for the former, indicating that larval mortality was greater for Cx pipiens. Both mosquito species showed a higher container index (CI) in shaded than in sunlit containers (Ae. aegypti: 12.8% vs. 6.9% [chi(2) = 17.6, P < 0.001]; Cx pipiens: 6.3% vs. 1.8% [chi(2) = 24, P < 0.001]). However, the number and the density of immatures per infested container and the number of pupae per pupa-positive container did not differ significantly between sunlit and shaded containers for either species. Therefore, the overall relative productivity of pupae per ha of Ae. aegypti and Cx pipiens was 2.3 and 1.8 times greater, respectively, in shaded than in sunlit areas as a result of the greater CIs of containers in shaded areas. Neither the CI nor the number of immatures per infested container differed significantly among container types of different materials in either lighting condition. The maximum CI and total pupal counts occurred in March for Ae. aegypti and in January and February for Cx pipiens. The estimated peak abundance of pupae in the whole cemetery reached a total of approximately 4388 in the middle of March for Ae. aegypti and approximately 1059 in the middle of January for Cx pipiens. Spearman's correlations between monthly total productivity and monthly CI were significant at P < 0.001 for Ae. aegypti (r(s) = 0.975) and P < 0.01 for Cx pipiens (r(s) = 0.869). Our findings indicate that the efficacy of control campaigns against the two most important mosquito vectors in temperate Argentina could be improved by targeting containers in shaded areas, with maximum effort during species-specific times of year when pupal productivity is at its peak.

Heartworm disease in animals and humans

Heartworm disease due to Dirofilaria immitis continues to cause severe disease and even death in dogs and other animals in many parts of the world, even though safe, highly effective and convenient preventatives have been available for the past two decades. Moreover, the parasite and vector mosquitoes continue to spread into areas where they have not been reported previously. Heartworm societies have been established in the USA and Japan and the First European Dirofilaria Days (FEDD) Conference was held in Zagreb, Croatia, in February of 2007. These organizations promote awareness, encourage research and provide updated guidelines for the diagnosis, treatment and prevention of heartworm disease. The chapter begins with a review of the biology and life cycle of the parasite. It continues with the prevalence and distribution of the disease in domestic and wild animals, with emphasis on more recent data on the spreading of the disease and the use of molecular biology techniques in vector studies. The section on pathogenesis and immunology also includes a discussion of the current knowledge of the potential role of the Wolbachia endosymbiont in inflammatory and immune responses to D. immitis infection, diagnostic use of specific immune responses to the bacteria, immunomodulatory activity and antibiotic treatment of infected animals. Canine, feline and ferret heartworm disease are updated with regard to the clinical presentation, diagnosis, prevention, therapy and management of the disease, with special emphasis on the recently described Heartworm Associated Respiratory Disease (HARD) Syndrome in cats. The section devoted to heartworm infection in humans also includes notes on other epizootic filariae, particularly D. repens in humans in Europe. The chapter concludes with a discussion on emerging strategies in heartworm treatment and control, highlighting the potential role of tetracycline antibiotics in adulticidal therapy.

Are antigen test kits efficient for detecting heartworm-infected dogs at the southern distribution limit of the parasite in South America? Preliminary results

The aim of this study was to evaluate the performance of commercial heartworm antigen tests in dogs harbouring Dirofilaria immitis microfilariae near its distribution limit in South America. A total of 4934 blood samples of adult dogs from Southern Greater Buenos Aires were examined to detect circulating microfilariae in the buffy coat interface between December 2005 and April 2006. Microfilariae were detected in 88 (1.8%) blood samples and all the microfilariae observed were identified as D. immitis by acid phosphatase stain technique. In a first trial, 69 (78.4%) out of the 88 serum were positive by Speed((R)) Diro. Then, a new test was performed over 25 microfilariae-positive serum samples randomly selected among the 88 previously tested samples and using simultaneously Speed((R)) Diro, Witness((R)) Dirofilaria and Snap((R)) 3dx. This second trial showed identical results for the three different tests, in which 19 (76%) samples were positive. Therefore, more than 20% of microfilaremic dogs were antigen negative. The main hypothesis that could explain our finding is a low worm burden in the study area. According to our preliminary results, it is highly recommendable the complementary use of antigen tests and other procedures to obtain an accurate diagnostic near the distribution limit of the parasite.

Predicting the spatial distribution of Ochlerotatus albifasciatus (Diptera: Culicidae) abundance with NOAA imagery

Ochlerotatus albifasciatus is a vector of western equine encephalomyelitis in Argentina and a nuisance mosquito affecting beef and dairy production. The objective of this study was to analyze whether environmental proxy data derived from 1 km resolution NOAA-AVHRR images could be useful as a rapid tool for locating areas with higher potential for Oc. albifasciatus activity at a regional scale. Training sites for mosquito abundance categories were 3.3x3.3 km polygons over sampling sites. Abundance was classified into two categories according to a proposed threshold for economic losses. Data of channels 1, 2, 4 and 5 were used to calculate five biophysical variables: normalized differences vegetation index (NDVI), land surface temperature, total precipitable water, dew point and vapour saturation deficit. A discriminant analysis correctly classified 100% of the areas predicted to be above or below the economic threshold of 2500 mosquitoes per night of capture, respectively. Components of the NDVI, the total precipitable water and the dew point temperature contributed most to the function value. The results suggest that environmental data derived from AVHRR-NOAA could be useful for rapidly identifying adequate areas for mosquito development or activity.

Prevalence and epidemiological aspects of Dirofilaria immitis in dogs from Kayseri Province, Turkey

This study was conducted to determine the prevalence of Dirofilaria immitis infection and to investigate the risk factors related to heartworm disease in dogs from Kayseri, Turkey. Blood samples were collected from 280 dogs from May 2005 to March 2006 and were examined by membrane filtration-acid phosphatase histochemical staining and antigen Elisa techniques to detect circulating microfilariae and antigens of D. immitis, respectively. Of the total of 280 dogs, 27 were positive for D. immitis with a prevalence value of 9.6%. In addition 29.6% of positive dogs determined to have occult D. immitis infections. D. immitis was the only canine filarial parasite present in the study area. The mean number of microfilariae in infected dogs was 4730+/-5479 per ml of blood. The highest heartworm prevalence were observed in 7-10 age group (28.6%) followed by 4-6 (17.1%) and 0.5-3 (4.8%) age groups. The differences between 0.5-3 and other age groups were found significant, whereas no statistically significant difference was observed between 4-6 and 7-10 age groups. The infection was more prevalent in males, larger breeds and the dogs not on prophylaxis. No statistically significant difference was observed between stray and owned dogs. Our results suggest that heartworm treatment and prophylaxis should be considered in Kayseri Province.

Spatial and temporal transmission risk of Dirofilaria immitis in Argentina

The aim of this work was to assess spatial and seasonal Dirofilaria immitis transmission risk throughout Argentina with models based on the temperature threshold below which filarial development will not proceed in the mosquito (i.e. 14 degrees C), the occurrence and the number of potential vector mosquito species, and the Heartworm Development Units derived from the degree-days concept. The four models showed a similar increasing southwest-northeast tendency and correlated significantly with canine prevalences used as external validation data. About one-third of Argentina would be suitable for heartworm transmission and the highest risk areas include the north-eastern provinces. According to our models, heartworm transmission is markedly seasonal with peaks in January and February; no region would support transmission throughout the year. To improve the present models, it is necessary to know which mosquito species are competent rather than potential vectors in the country. We believe the present study provides the first risk assessment maps for D. immitis transmission in the Southern Hemisphere and provides a useful guide for heartworm prevention during the transmission periods in different regions of Argentina.