First record of Dioctophyme renale (Goeze, 1782) in the pampas fox (Lycalopex gymnocercus, Fischer, 1814) (Carnivora: Canidae).

Dioctophyme renale (Goeze 1782) has not previously been reported in the pampas fox (Lycalopex gymnocercus) (Fisher 1814), the most abundant canid of southern South America. A wild adult pampas fox female was found dead due to unknown causes in Santa Fe province, Argentina. Post-mortem examination revealed three red worms measuring 10, 11 and 15 cm long, each with an approximate width of 5 mm. All of them were found free in the abdominal cavity. The worms were all male and were identified through morphological examination and molecular analysis as D. renale. No worm was found in the kidneys. This study reports the first case of dioctophymatosis in the pampas fox in Argentina, increasing the range of wild aberrant host species infected by the giant kidney worm in the Neotropical region.

Ecological factors shaping the ectoparasite community assembly of the Azara's Grass Mouse, Akodon azarae (Rodentia: Cricetidae).

Parasites are integral members of the global biodiversity. They are useful indicators of environmental stress, food web structure and diversity. Ectoparasites have the potential to transmit vector-borne diseases of public health and veterinary importance and to play an important role in the regulation and evolution of host populations. The interlinkages between hosts, parasites and the environment are complex and challenging to study, leading to controversial results. Most previous studies have been focused on one or two parasite groups, while hosts are often co-infected by different taxa. The present study aims to assess the influence of environmental and host traits on the entire ectoparasite community composition of the rodent Akodon azarae. A total of 278 rodents were examined and mites (Mesostigmata), lice (Phthiraptera), ticks (Ixodida) and fleas (Siphonaptera) were determined. A multi-correspondence analysis was performed in order to analyze interactions within the ectoparasite community and the influence of environmental and host variables on this assembly. We found that environmental variables have a stronger influence on the composition of the ectoparasite community of A. azarae than the host variables analyzed. Minimum temperature was the most influential variable among the studied. In addition, we found evidence of agonistic and antagonistic interactions between ticks and mites, lice and fleas. The present study supports the hypothesis that minimum temperature plays a major role in the dynamics that shape the ectoparasite community of A. azarae, probably through both direct and indirect processes. This finding becomes particularly relevant in a climate change scenario.

Specialist by preference, generalist by need: availability of quality hosts drives parasite choice in a natural multihost-parasite system.

Encountering suitable hosts is key for parasite success. A general assumption for disease transmission is that the contact of a parasite with a potential host is driven by the density or relative frequency of hosts. That assumption ignores the potential role of differential host attractiveness for parasites that can drive the encounter of hosts. It has been posited that hosts may be chosen by parasites as a function of their suitability, but the existing literature addressing that hypothesis is still very scarce. In a natural system involving a parasitic Philornis botfly and its multiple bird hosts, there are profound differences in host quality. The Great Kiskadee tolerates and does not invest in resisting the infection, which makes it an optimal host. Alternative hosts are frequently used, but whilst some of them may be good options, others are bad alternatives. Here we examined the host selection processes that drive parasite dynamics in this system with 8 years of data from a longitudinal study under natural conditions. We found that the use of an alternative host was not driven by its density or relative frequency, but instead selection of these hosts was strongly dependent on availability of more suitable hosts. When optimal hosts are plentiful, the parasite tends to ignore alternative ones. As broods of optimal hosts become limited, good alternative hosts are targeted. The parasite chooses bad alternative hosts only when better alternatives are not sufficiently available. These results add evidence from a natural system that some parasites choose their hosts as a function of their profitability, and show that host selection by this parasite is plastic and context-dependent. Such findings could have important implications for the epidemiology of some parasitic and vector-borne infections which should be considered when modelling and managing those diseases. The facultative host selection observed here can be of high relevance for public health, animal husbandry, and biodiversity conservation, because reductions in the richness of hosts might cause humans, domestic animals, or endangered species to become increasingly targeted by parasites that can drive the encounter of hosts.

Chronic exposure to environmental stressors enhances production of natural and specific antibodies in rats.

Although the immunosuppressive effect of chronic stress has been established, a stress response that downregulates the whole immune system does not make biological sense, especially if an animal has to endure difficult times in which there is also increased infection risk. At high animal densities, animals are faced simultaneously with food restriction (FR), social conflict (SC), and greater parasite-pathogen exposure. We hypothesized that the stress response to chronic stressors that covary with infection risk is not entirely immunosuppressive. Our prediction was that a chronically stressed animal would respond by enhancing innate defenses, while reducing investment in acquired immunity. In a laboratory setting, rats were exposed to prolonged FR and/or SC, and natural and specific antibody levels were repeatedly measured. Our prediction was fulfilled only partly, as FR and SC interacted to enhance natural antibodies, but rats exposed to either or both stressors also showed significantly higher levels of specific antibodies. These results suggest that, in the rat, chronic stress results in a prioritization of both innate and acquired humoral defenses, which makes biological sense provided the stressors examined usually signal an increased infection risk.

New host species for Leptospira borgpetersenii and Leptospira interrogans serovar Copenhageni.

We investigated the presence of infection by Leptospira spp. in an assembly of Sigmodontinae rodents from the Paraná Delta, Argentina. Rodents were captured in places with natural grassland, implanted forest, with and without raising cattle and in sites prone and not prone to flooding. The DNA was amplified from cultured isolates by PCR and Leptospira spp. strains were genotyped using Multiple - Locus Variable Number Tandem Repeat Analysis (MLVA). We isolated Leptospira interrogans serovar Copenhageni from Oligoryzomys nigripes, Leptospira borgpetersenii from Scapteromys aquaticus and Leptospira interrogans serovar Icterohaemorrhagiae from Akodon azarae. The zoonotic Leptospira isolated and genotyped from O. nigripes and S. aquaticus are the first reports from these species. The geographic range of these rodent species include, in addition to Argentina, the countries of Paraguay, Uruguay and Brazil, suggesting that these rodents might be involved in the transmission of spirochetes in other regions. Human and animal health care professionals should be alert to the potential occurrence of leptospirosis in areas where these rodent species are present.

Reprint of "Survey and first molecular characterization of Echinococcus granulosus sensu stricto (G1) in Pampas fox (Lycalopex gymnocercus) in Buenos Aires province, Argentina".

Echinococcosis is a zoonosis caused by tapeworms of the genus Echinococcus. Echinococcus granulosus sensu lato (s. l.) has a world-wide distribution and its transmission is primarily maintained in a synanthropic cycle with dogs as definitive hosts and livestock species as intermediate hosts. However, many wild canids also function as definitive hosts for E. granulosus s. l. Echinococcosis in humans is mainly caused by E. granulosus sensu stricto (s. s.) G1 genotype. In the present work, we expanded the epidemiological study on echinococcosis reported cases in Pampas fox (Lycalopex gymnocercus) to provide a prevalence estimate for rural areas of southern Buenos Aires province, Argentina. Ninety-five whole intestines were analyzed using the sedimentation and counting technique with a result of 83 foxes (87.37%) harboring at least one helminth species. E. granulosus s. l. adults were found in one Pampas fox (1.05%). These adult helminthes were E. granulosus s. s. (G1) according to the genotyping analysis of a 450-bp region of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene.

Ancylostoma (Ancylostoma) buckleyi (Nematoda: Ancylostomatidae): new wild host and distribution expansion.

Here we report the occurrence of Ancylostoma (Ancylostoma) buckleyi (Le Roux and Biocca, 1957) (Nematoda: Ancylostomatidae) in the small intestine of Pampas foxes (Lycalopex gymnocercus) (Mammalia: Canidae). This fox is the most abundant native carnivore in southern South America, where it inhabits grasslands, open woodlands and areas highly modified by extensive ranching and agricultural activities. Material from 80 foxes in rural areas of southern Buenos Aires province, Argentina was examined. The intestinal tracts were carefully removed from each carcass and subsequently isolated by ligatures (pylorus and rectum). Examination of the intestinal content was performed using the sedimentation and counting technique. Four foxes (5%) were found to be parasitized with adult specimens of A. buckleyi. This is the first report of Ancylostoma (A.) buckleyi in Argentina and adds L. gymnocercus as new host of this nematode species.

Ancylostoma (Ancylostoma) buckleyi (Nematoda: Ancylostomatidae): new wild host and distribution expansion / Ancylostoma (Ancylostoma) buckleyi (Nematoda: Ancylostomatidae): novo hospedeiro salvagem e expansão de distribuição

Abstract Here we report the occurrence of Ancylostoma (Ancylostoma) buckleyi (Le Roux and Biocca, 1957) (Nematoda: Ancylostomatidae) in the small intestine of Pampas foxes (Lycalopex gymnocercus) (Mammalia: Canidae). This fox is the most abundant native carnivore in southern South America, where it inhabits grasslands, open woodlands and areas highly modified by extensive ranching and agricultural activities. Material from 80 foxes in rural areas of southern Buenos Aires province, Argentina was examined. The intestinal tracts were carefully removed from each carcass and subsequently isolated by ligatures (pylorus and rectum). Examination of the intestinal content was performed using the sedimentation and counting technique. Four foxes (5%) were found to be parasitized with adult specimens of A. buckleyi. This is the first report of Ancylostoma (A.) buckleyi in Argentina and adds L. gymnocercus as new host of this nematode species.

Resumo O presente estudo relata a ocorrência de Ancylostoma (Ancylostoma) buckleyi (Le Roux and Biocca, 1957) (Nematoda: Ancylostomatidae) no intestino delgado do Graxaim do campo (Lycalopex gymnocercus) (Mammalia: Canidae). Essa raposa é o carnívoro nativo mais abundante no sul da América do Sul, onde habita nas pastagens, florestas abertas e áreas altamente modificadas pelas atividades pecuária extensiva e agrícola. Material de 80 raposas, em áreas rurais do sul da província de Buenos Aires, Argentina, foi examinado. Os tratos intestinais foram cuidadosamente removidos de cada carcaça e, posteriormente, isolados por ligaduras (piloro e reto). O exame do conteúdo intestinal foi realizado, utilizando-se a técnica de sedimentação e contagem. Quatro raposas (5%) foram encontradas parasitadas com espécimes adultos de A. buckleyi. O estudo registra, pela primeira vez, a ocorrência de Ancylostoma (A.) buckleyi na Argentina e adiciona L. gymnocercus como novo hospedeiro dessa espécie de nematoides.

Survey and first molecular characterization of Echinococcus granulosus sensu stricto (G1) in Pampas fox (Lycalopex gymnocercus) in Buenos Aires province, Argentina.

Echinococcosis is a zoonosis caused by tapeworms of the genus Echinococcus. Echinococcus granulosus sensu lato (s. l.) has a world-wide distribution and its transmission is primarily maintained in a synanthropic cycle with dogs as definitive hosts and livestock species as intermediate hosts. However, many wild canids also function as definitive hosts for E. granulosus s. l. Echinococcosis in humans is mainly caused by E. granulosus sensu stricto (s. s.) G1 genotype. In the present work, we expanded the epidemiological study on echinococcosis reported cases in Pampas fox (Lycalopex gymnocercus) to provide a prevalence estimate for rural areas of southern Buenos Aires province, Argentina. Ninety-five whole intestines were analyzed using the sedimentation and counting technique with a result of 83 foxes (87.37%) harboring at least one helminth species. E. granulosus s. l. adults were found in one Pampas fox (1.05%). These adult helminthes were E. granulosus s. s. (G1) according to the genotyping analysis of a 450-bp region of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene.

New hosts and localities for helminths of carnivores in Argentina.

A total of 111 samples (43 faeces and 79 gastrointestinal tracts) of 14 wild carnivore species from 12 Argentine provinces were analyzed. Helminth eggs were identified in 73% of the faecal samples and adult worms were recovered from 81% of the gastrointestinal tracts. We found 19 helminth species. Among the most frequent findings were parasites of domestic carnivores, namely Toxocara canis, Toxocara cati, Toxascaris leonina, Ancylostoma caninum, Ancylostoma tubaeforme and Uncinaria stenocephala. In addition, new hosts are reported for 6 nematode species and 5 helminth species are recorded for the first time in Argentina: Aonchotheca putorii, Molineus brachiurus, Cyathospirura chevreuxi, Physaloptera praeputialis and Oncicola martini.

The Pampas fox (Lycalopex gymnocercus) as new definitive host for Spirometra erinacei (Cestoda: Diphyllobothriidae).

Spirometra erinacei, Faust, Campbell and Kellogg, 1929, is a pseudophyllidean cestode of the family Diphyllobothriidae. The genus Spirometra is cosmopolitan and these parasites infect carnivores, specially felids and canids. In Argentina, S. erinacei and S. mansonoides have been reported sporadically only in domestic definitive hosts. The Pampas fox, Lycalopex gymnocercus, is the most abundant native carnivore in southern South America, where it inhabits grasslands and open woodlands and areas highly modified by extensive ranching and agricultural activities. This report describes the first finding of S. erinacei infecting Pampas fox, and provides an estimate prevalence of this cestode in rural areas of southern Buenos Aires province, Argentina based on 78 complete Pampas fox intestine samples analysis. This study found a 15.4% of prevalence of S. erinacei in small intestine (adult stage) and a 21.8% in fecal samples (egg stage). In the present work, the first case of S. erinacei in a wild definitive host from Argentina was reported expanding the list of definitive hosts of S. erinacei in South America.

Epidemiological studies on Echinococcus in Pampas fox (Lycalopex gymnocercus) and European hare (Lepus europaeus) in Buenos Aires province, Argentina.

In Argentina, hydatid disease caused by Echinococcus granulosus is widespread. The south of Buenos Aires province, Argentina, is one of the three regions where hydatidosis is endemic. Although domestic dogs and sheep are considered to be the main hosts for E. granulosus, the potential role of wildlife in the local transmission of E. granulosus has not been investigated. The aim of this study was to estimate the hydatidosis/echinococcosis prevalence in European hare (Lepus europaeus) and Pampas fox (Lycalopex gymnocercus), two abundant species with a strong predator-prey relationship in rural areas of Buenos Aires province using different diagnostic tests. A total of 61 fox intestines were examined, finding that 52 (85.2%) harbored at least one helminth species. However, no adult or immature form of Echinococcus sp. was found in the intestinal contents. Coproparasitological analysis and Copro-ELISA followed by Copro-PCR were used as supplementary diagnostic tests. Only one (1.7%) of 59 fecal samples was positive to Taeniidae eggs by coproparasitological analysis, but this same sample was negative by the Copro-ELISA test. The analysis by Copro-ELISA showed 6 of 57 (10.6%) positive samples, but the Copro-PCR tests carried out on these samples were negative to E. granulosus. A total of 6,808 lungs, 3,576 livers, and 3,542 hearts of hunted hares were examined and palpated, but no structure resembling hydatid cysts were detected. Our results suggest that hares and Pampas foxes are not currently important wild reservoirs of E. granulosus in the studied area.

Multi-level determinants of parasitic fly infection in forest passerines.

The study of myiasis is important because they may cause problems to the livestock industry, public health, or wildlife conservation. The ecology of parasitic dipterans that cause myiasis is singular, as they actively seek their hosts over relatively long distances. However, studies that address the determinants of myiasis dynamics are very scarce. The genus Philornis include species that may be excellent models to study myiasis ecology, as they exclusively parasitize bird nestlings, which stay in their nests until they are fully fledged, and larvae remain at the point of entry until the parasitic stage is over, thus allowing the collection of sequential individual-level infection data from virtually all the hosts present at a particular area. Here we offer a stratified multi-level analysis of longitudinal data of Philornis torquans parasitism in replicated forest bird communities of central Argentina. Using Generalized Linear Models and Generalized Linear Mixed Models and an information theory approach for model selection, we conducted four groups of analyses, each with a different study unit, the individual, the brood, the community at a given week, and the community at a given year. The response variable was larval abundance per nestling or mean abundance per nestling. At each level, models included the variables of interest of that particular level, and also potential confounders and effect modifiers of higher levels. We found associations of large magnitude at all levels, but only few variables truly governed the dynamics of this parasite. At the individual level, the infection was determined by the species and the age of the host. The main driver of parasite abundance at the microhabitat level was the average height of the forest, and at the community level, the density of hosts and prior rainfall. This multi-level approach contributed to a better understanding of the ecology of myiasis.

Redescription of Echinocoleus hydrochoeri (Travassos, 1916) (Nematoda: Trichuridae) from Hydrochoeris hydrochaeris Linnaeus, 1766 (Rodentia: Caviidae) from Argentina.

Twenty-eight Capillariinae species have been recorded in rodents; 1 of these species was reported from a caviomorph rodent, Hydrochoeris hydrochaeris (capybara), and placed in the genus Echinocoleus by Moravec (1982). However, both original description and subsequent contributions of Echinocoleus hydrochoeri are poor and incomplete. In this paper, this species is redescribed, and a new geographical distribution is reported. The redescription is based on morphologic and morphometrical features; intestine ends in a cloaca beside ejaculatory duct, caudal bursa composed of 2 large ventrolateral lobes with a fleshy internal part and a membranous external part (they are not united dorsally with a membrane), 1 pair of caudal papillae, terminal part of cylindrical cirrus ornamented with thin and thick spines (and particular pattern distribution), sclerotized spicule in male, and vulvar appendage in female, and 3 bacillary bands (1 ventral and 2 lateral). Generic and specific analyses were performed to establish new standards for future studies on the systematic position of Capillariinae species. This study presents new morphological information and a new record of a capillariid species from Argentina.

Ixodes (Ixodes) pararicinus Keirans & Clifford, 1985 (Acari: Ixodidae): description of the immature stages, distribution, hosts and medical/veterinary importance.

The immature stages of the Neotropical tick Ixodes (Ixodes) pararicinus Keirans & Clifford, 1985 are described from specimens in a laboratory colony initiated from engorged females collected on cattle and larvae fed on mice and chickens. The larva and nymph of I. pararicinus are described using SEM micrographs as well as drawings for some features of the larva. Additionally, immature stages of I. pararicinus collected on wild mice and birds in Uruguay and Argentina were compared with specimens from the laboratory colony. A taxonomic key to the nymphs of the species of the ricinus complex established in the Western Hemisphere is presented. The distribution of I. pararicinus comprises Argentina, Colombia and Uruguay, but it is also probably established in Bolivia, Brazil, Chile and Peru. Most adult ticks of this species have been found on introduced domestic artiodactyles, although Neotropical deer species must have been the ancestral host. Larvae and nymphs of I. pararicinus have also been found on sigmodontine rodents and passeriform birds. Although I. pararicinus is a member of the ricinus complex, which contains the main vectors of Borrelia burgdorferi (sensu lato), there are few studies concerning its potential for pathogen transmission.

Ixodes (Ixodes) pararicinus Keirans & Clifford, 1985 (Acari: Ixodidae) description of the immature stages, distribution, hosts and medical veterinary importance

The immature stages of the Neotropical tick Ixodes (Ixodes) pararicinus Keirans & Clifford, 1985 are describedfrom specimens in a laboratory colony initiated from engorged females collected on cattle and larvaefed on mice and chickens. The larva and nymph of I. pararicinus are described using SEM micrographs as wellas drawings for some features of the larva. Additionally, immature stages of I. pararicinus collected on wildmice and birds in Uruguay and Argentina were compared with specimens from the laboratory colony. Ataxonomic key to the nymphs of the species of the ricinus complex established in the Western Hemisphere ispresented. The distribution of I. pararicinus comprises Argentina, Colombia and Uruguay, but it is alsoprobably established in Bolivia, Brazil, Chile and Peru. Most adult ticks of this species have been found onintroduced domestic artiodactyles, although Neotropical deer species must have been the ancestral host.Larvae and nymphs of I. pararicinus have also been found on sigmodontine rodents and passeriformbirds. Although I. pararicinus is a member of the ricinus complex, which contains the main vectors ofBorrelia burgdorferi (sensu lato), there are few studies concerning its potential for pathogen transmission.

Capillariidae eggs found in the urine of a free ranging maned wolf from Argentina.

The first finding of a Capillariid in the urinary tract of a free ranging maned wolf (Chrysocyon brachyurus) is described. The individual was an adult male attacked by dogs in the locality of Cayastacito (Santa Fe, Argentina, 31 degrees 05' S, 60 degrees 34' W). Eggs found in urine measured 64.6-66.9 micrometer (mean 65.4 micrometer) x 26.9-31 micrometer (mean 29 micrometer). Further studies are needed to determine whether this finding corresponds to a new Capillariid species, related to C. brachyurus, or it is an already described species that has been introduced by domestic dogs.