Social network structure and parasite infection patterns in a territorial reptile, the tuatara (Sphenodon punctatus)

We investigated whether the parasite load of an individual could be predicted by its position in a social network. Specifically, we derived social networks in a solitary, territorial reptile (the tuatara, Sphenodon punctatus), with links based on the sharing of space, not necessarily synchronously, in overlapping territories. Tuatara are infected by ectoparasitic ticks (Amblyomma sphenodonti), mites (Neotrombicula spp.) and a blood parasite (Hepatozoon tuatarae) which is transmitted by the tick. We recorded the location of individual tuatara in two study plots twice daily during the mating season (March) in 2 years (2006 and 2007) on Stephens Island, New Zealand. We constructed weighted, directed networks to represent pathways for parasite transmission, where nodes represented individual tuatara and edges connecting the nodes represented the extent of territory overlap among each pair of individuals. We considered a network-based hypothesis which predicted that the in-strength of individuals (the sum of edge weights directed towards a node) in the derived network would be positively related to their parasite load. Alternatively, if the derived social network did not reflect actual parasite transmission, we predicted other factors such as host sex, size or territory size may better explain variation in parasite infection patterns. We found clear positive relationships between the in-strength of tuatara and their tick loads, and infection patterns with tick-borne blood parasites. In particular, the extent that individuals were connected to males in the network consistently predicted tick loads of tuatara. However, mite loads of tuatara were significantly related to host sex, body size and territory size, and showed little association with network measures. The results suggest that the pathway of transmission of parasites through a population will depend on the transmission mechanism of the parasite, but that social networks provide a powerful predictive tool for some parasites.     

Seasonal and spatial dynamics of ectoparasite infestation of a threatened reptile, the tuatara (Sphenodon punctatus)

Abstract The conservation of threatened vertebrate species and their threatened parasites requires an understanding of the factors influencing their distribution and dynamics. This is particularly important for species maintained in conservation reserves at high densities, where increased contact among hosts could lead to increased rates of parasitism. The tuatara (Sphenodon punctatus) (Reptilia: Sphenodontia) is a threatened reptile that persists at high densities in forests (～ 2700 tuatara/ha) and lower densities in pastures and shrubland (< 200 tuatara/ha) on Stephens Island, New Zealand. We investigated the lifecycles and seasonal dynamics of infestation of two ectoparasites (the tuatara tick, Amblyomma sphenodonti, and trombiculid mites, Neotrombicula sp.) in a mark‐recapture study in three forest study plots from November 2004 to March 2007, and compared infestation levels among habitat types in March 2006. Tick loads were lowest over summer and peaked from late autumn (May) until early spring (September). Mating and engorgement of female ticks was highest over spring, and larval tick loads subsequently increased in early autumn (March). Nymphal tick loads increased in September, and adult tick loads increased in May. Our findings suggest the tuatara tick has a 2‐ or 3‐year lifecycle. Mite loads were highest over summer and autumn, and peaked in March. Prevalences (proportion of hosts infected) and densities (estimated number of parasites per hectare) of ticks were similar among habitats, but tick loads (parasites per host) were higher in pastures than in forests and shrub. The prevalence and density of mites was higher in forests than in pasture or shrub, but mite loads were similar among habitats. We suggest that a higher density of tuatara in forests may reduce the ectoparasite loads of individuals through a dilution effect. Understanding host–parasite dynamics will help in the conservation management of both the host and its parasites.     

Host–parasite interactions and vectors in the barn swallow in relation to climate change

Recent climate change has affected the phenology of numerous species, and such differential changes may affect host–parasite interactions. Using information on vectors (louseflies, mosquitoes, blackflies) and parasites (tropical fowl mite Ornithonyssus bursa, the lousefly Ornithomyia avicularia, a chewing louse Brueelia sp., two species of feather mites Trouessartia crucifera and Trouessartia appendiculata, and two species of blood parasites Leucozytozoon whitworthi and Haemoproteus prognei) of the barn swallow Hirundo rustica collected during 1971–2008, I analyzed temporal changes in emergence and abundance, relationships with climatic conditions, and changes in the fitness impact of parasites on their hosts. Temperature and rainfall during the summer breeding season of the host increased during the study. The intensity of infestation by mites decreased, but increased for the lousefly during 1982–2008. The prevalence of two species of blood parasites increased during 1988–2008. The timing of first mass emergence of mosquitoes and blackflies advanced. These temporal changes in phenology and abundance of parasites and vectors could be linked to changes in temperature, but less so to changes in precipitation. Parasites had fitness consequences for hosts because intensity of the mite and the chewing louse was significantly associated with delayed breeding of the host, while a greater abundance of feather mites was associated with earlier breeding. Reproductive success of the host decreased with increasing abundance of the chewing louse. The temporal decrease in mite abundance was associated with advanced breeding of the host, while the increase in abundance of the lousefly was associated with earlier breeding. Virulence by the tropical fowl mite decreased with increasing temperature, independent of confounding factors. These findings suggest that climate change affects parasite species differently, hence altering the composition of the parasite community, and that climate change causes changes in the virulence of parasites. Because the changing phenology of different species of parasites had both positive and negative effects on their hosts, and because the abundance of some parasites increased, while that of other decreased, there was no consistent temporal change in host fitness during 1971–2008.     

Why Lyme disease is common in the northern US,but rare in the south: The roles of host choice,host-seeking behavior,and tick density

Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks must acquire Lyme spirochetes from infected vertebrate hosts, the role of wildlife species composition on Lyme disease risk has been a topic of lively academic discussion. We compared tick–vertebrate host interactions using standardized sampling methods among 8 sites scattered throughout the eastern US. Geographical trends in diversity of tick hosts are gradual and do not match the sharp decline in prevalence at southern sites, but tick–host associations show a clear shift from mammals in the north to reptiles in the south. Tick infection prevalence declines north to south largely because of high tick infestation of efficient spirochete reservoir hosts (rodents and shrews) in the north but not in the south. Minimal infestation of small mammals in the south results from strong selective attachment to lizards such as skinks (which are inefficient reservoirs for Lyme spirochetes) in the southern states. Selective host choice, along with latitudinal differences in tick host-seeking behavior and variations in tick densities, explains the geographic pattern of Lyme disease in the eastern US.

Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. This study shows that this is largely because the tick vectors attach abundantly to rodents (which are good hosts for the Lyme bacteria) in the north, and to lizards (which are relatively poor hosts for Lyme bacteria) in the south.     

Prevalence and host-parasite list of some nasal mites from birds (Acarina: Rhinonyssidae, Speleognathidae)

A survey of nasal mites, primarily from birds in Texas, was reported and comparisons with the other major studies were made. Of 103 host species examined, 40 were parasitized, and of 502 individual birds examined, 87 were parasitized (17% prevalence). It was shown that the prevalence of infection was significantly dependent on the bird taxa examined, which indicates that the evolution of the hosts has affected the nasal mites' ability to parasitize their avian hosts. It was also shown that the prevalence of rhinonyssid nasal mites in their hosts seems to differ significantly between geographic regions.     

The role of host traits, season and group size on parasite burdens in a cooperative mammal

The distribution of parasites among hosts is often characterised by a high degree of heterogeneity with a small number of hosts harbouring the majority of parasites. Such patterns of aggregation have been linked to variation in host exposure and susceptibility as well as parasite traits and environmental factors. Host exposure and susceptibility may differ with sexes, reproductive effort and group size. Furthermore, environmental factors may affect both the host and parasite directly and contribute to temporal heterogeneities in parasite loads. We investigated the contributions of host and parasite traits as well as season on parasite loads in highveld mole-rats (Cryptomys hottentotus pretoriae). This cooperative breeder exhibits a reproductive division of labour and animals live in colonies of varying sizes that procreate seasonally. Mole-rats were parasitised by lice, mites, cestodes and nematodes with mites (Androlaelaps sp.) and cestodes (Mathevotaenia sp.) being the dominant ecto- and endoparasites, respectively. Sex and reproductive status contributed little to the observed parasite prevalence and abundances possibly as a result of the shared burrow system. Clear seasonal patterns of parasite prevalence and abundance emerged with peaks in summer for mites and in winter for cestodes. Group size correlated negatively with mite abundance while it had no effect on cestode burdens and group membership affected infestation with both parasites. We propose that the mode of transmission as well as social factors constrain parasite propagation generating parasite patterns deviating from those commonly predicted.     

Microhabitat choice and host-seeking behaviour of the tuatara tick,

Understanding the factors that influence patterns of ectoparasite infestation within wildlife populations involves knowledge of the mechanisms that influence host infestation. For ectoparasitic ticks, knowing where ticks might occur in the off-host environment and how they locate their hosts is essential to understanding patterns of ectoparasite infestation. The tuatara tick (Amblyomma sphenodonti) parasitises the tuatara (Sphenodon punctatus) on Stephens Island, New?Zealand. We completed a series of laboratory microcosm experiments to examine daily activity patterns, microhabitat preferences and host-seeking behaviour by Amblyomma sphenodonti. Firstly, to determine the diel activity pattern of ticks, we observed the behaviour of ticks every 2?h over a 48-h period. We then tested the preferences of ticks for soil moisture, soil texture and shade by offering different pairs of substrate conditions. Last, to determine what cues ticks used to locate their hosts, we tested the response of ticks to filter paper infused with host scent or excrement. Ticks were most active at night. They also showed a significant preference for moister, coarser and shaded substrates 12 h after the start of the experiment. Ticks did not show an immediate response to either of the two host stimuli, but after 12 h showed a significant preference for host scent and avoided host excreta. We suggest that the microhabitat preferences of ticks reflect conditions within host refuges (burrows), and that the delayed response to host odour suggests ticks could use host scent to identify substrates frequented by hosts.     

Co-occurrence of ectoparasites on rodent hosts: null model analyses of data from three continents

We studied patterns of species co-occurrence in communities of ectoparasitic arthropods (ixodid ticks, mesostigmate mites and fleas) harboured by rodent hosts from South Africa ( Rhabdomys pumilio ), South America ( Scapteromys aquaticus and Oxymycterus rufus ) and west Siberia ( Apodemus agrarius , Microtus gregalis , Microtus oeconomus and Myodes rutilus ) using null models. We compared frequencies of co-occurrences of parasite species or higher taxa across host individuals with those expected by chance. When non-randomness of parasite co-occurrences was detected, positive but not negative co-occurrences of parasite species or higher taxa prevailed (except for a single sample of mesostigmate mites from O. rufus ). Frequency of detection of non-randomness of parasite co-occurrences differed among parasite taxa, being higher in fleas and lower in mites and ticks. This frequency differed also among host species independent of parasite taxon, being highest in Microtus species and lowest in O. rufus and S. aquaticus . We concluded that the pattern of species co-occurrence in ectoparasite communities on rodent hosts is predominantly positive, depends on life history of parasites and may be affected to a great extent by life history of a host.     

First detection of Anaplasma phagocytophilum in quill mites (Acari: Syringophilidae) parasitizing passerine birds

Forest passerine birds and their ectoparasites: Ixodes ricinus ticks and Syringophilidae quill mites were surveyed for infection with Anaplasma phagocytophilum in west-central Poland. Of 126 birds captured from May to June of 2002, 71 (56.3%) comprising eight species, hosted immature I. ricinus ticks. A total of 383 ticks and 71 blood samples collected from tick-infested birds were investigated by PCR. The pathogen was not detected in either bird-derived ticks or in blood samples. Among the captured birds, a total of 14 individuals representing four species hosted quill mites from the family Syringophilidae. Three of the 14 mite pools recovered from the 14 mite-infested birds harbored A. phagocytophilum DNA by amplifying both the epank1 and p44 gene. The PCR-positive pools originated from one blackbird and two starlings. The specific biology of syringophilid mites, which parasitize exclusively inside the quill of feathers, feeding on host subcutaneous fluids, implies that they must have acquired the pathogen from a bacteremic bird. These results provide the first indirect evidence that at least some passerine hosts are prone to develop systemic infection with A. phagocytophilum under natural conditions. Consequently, the infected quill mites may serve as a "biological marker" of past or current infection with the agent within birds.     

Recapture of male and female dragonflies in relation to parasitism by mites, time of season, wing length and wing cell symmetry

For aquatic mites parasitic on dragonflies, completion of their life cycle depends on their being returned to appropriate water bodies by their hosts, after completion of engorgement. We examined whether differences among hosts in timing of emergence or phenotypic attributes might affect their probability of return to an emergence pond, and hence success of mites. Parasitized males and females of the dragonfly Sympetrum obtrusum (Hagen) did not differ in overall recapture rates. Females that had wing cell symmetry and emerged early were more likely to be recaptured than females that emerged later or had wing cell asymmetry, but there were no consistent relations between these variables and parasitism by mites. No such relations between wing cell asymmetry, emergence date, and recapture likelihood were found for males. Using randomization tests, we found that mean intensities of Arrenurus planus (Marshall) mites at host emergence were the same for recaptured females and females not recaptured; however, males that were recaptured had lower mean intensities of mites at emergence than males not recaptured. Further, mature females carried more mites than mature males, and the latter had fewer mites than newlyemerged males not recaptured. Biases in detachment of engorging mites do not explain the differences in parasitism between mature males and females, nor the differences in mite numbers between mature males and newly emerged males that were not recaptured. Rather, heavily parasitized males appear to disperse or die and are not recaptured, which should have implications for dispersal of mites and fitness of male hosts.     

Recapture of male and female dragonflies in relation to parasitism by mites, time of season, wing length and wing cell symmetry

For aquatic mites parasitic on dragonflies, completion of their life cycle depends on their being returned to appropriate water bodies by their hosts, after completion of engorgement. We examined whether differences among hosts in timing of emergence or phenotypic attributes might affect their probability of return to an emergence pond, and hence success of mites. Parasitized males and females of the dragonfly Sympetrum obtrusum (Hagen) did not differ in overall recapture rates. Females that had wing cell symmetry and emerged early were more likely to be recaptured than females that emerged later or had wing cell asymmetry, but there were no consistent relations between these variables and parasitism by mites. No such relations between wing cell asymmetry, emergence date, and recapture likelihood were found for males. Using randomization tests, we found that mean intensities of Arrenurus planus (Marshall) mites at host emergence were the same for recaptured females and females not recaptured; however, males that were recaptured had lower mean intensities of mites at emergence than males not recaptured. Further, mature females carried more mites than mature males, and the latter had fewer mites than newly emerged males not recaptured. Biases in detachment of engorging mites do not explain the differences in parasitism between mature males and females, nor the differences in mite numbers between mature males and newly emerged males that were not recaptured. Rather, heavily parasitized males appear to disperse or die and are not recaptured, which should have implications for dispersal of mites and fitness of male hosts.     

Dioctophyme renale (Goeze, 1782) (Nematoda,Dioctophymidae) parasitic in mammals other than humans: A comprehensive review

A comprehensive review of the infection of mammals with the nematode Dioctophyme renale (Goeze, 1782) (Nematoda, Dioctophymidae) is presented. Mammals, including man, are the definitive hosts for this parasite. Several aspects of the infection with the parasite in mammals other than humans are critically evaluated: geographical distribution, host species recorded so far and the relative importance of the different hosts, location of parasites within the host, prevalence and intensity of the infection, diagnostic methods, pathology induced by the parasites, epidemiology and the methods of control and treatment. The authors provide an updated review about the infection, based on a extensive bibliographic search worldwide, and point out the most relevant aspects of the biology of the parasite as well as several research topics which need to be explored for a better understanding of the biology of this interesting and important parasitic nematode.     

Sleeping site ecology,but not sex,affect ecto- and hemoparasite risk,in sympatric,arboreal primates (<Emphasis Type="Italic">Avahi occidentalis</Emphasis> and <Emphasis Type="Italic">Lepilemur edwardsi</Emphasis>)

Background

A central question in evolutionary parasitology is to what extent ecology impacts patterns of parasitism in wild host populations. In this study, we aim to disentangle factors influencing the risk of parasite exposure by exploring the impact of sleeping site ecology on infection with ectoparasites and vector-borne hemoparasites in two sympatric primates endemic to Madagascar. Both species live in the same dry deciduous forest of northwestern Madagascar and cope with the same climatic constraints, they are arboreal, nocturnal, cat-sized and pair-living but differ prominently in sleeping site ecology. The Western woolly lemur (Avahi occidentalis) sleeps on open branches and frequently changes sleeping sites, whereas the Milne-Edward’s sportive lemur (Lepilemur edwardsi) uses tree holes, displaying strong sleeping site fidelity. Sleeping in tree holes should confer protection from mosquito-borne hemoparasites, but should enhance the risk for ectoparasite infestation with mites and nest-adapted ticks. Sex may affect parasite risk in both species comparably, with males bearing a higher risk than females due to an immunosuppressive effect of higher testosterone levels in males or to sex-specific behavior. To explore these hypotheses, ectoparasites and blood samples were collected from 22 individuals of A. occidentalis and 26 individuals of L. edwardsi during the dry and rainy season.

Results

L. edwardsi, but not A. occidentalis, harbored ectoparasites, namely ticks (Haemaphysalis lemuris [Ixodidae], Ornithodoros sp. [Argasidae]) and mites (Aetholaelaps trilyssa, [Laelapidae]), suggesting that sleeping in tree holes promotes infestation with ectoparasites. Interestingly, ectoparasites were found solely in the hot, rainy season with a prevalence of 75% (N = 16 animals). Blood smears were screened for the presence and infection intensity of hemoparasites. Microfilariae were detected in both species. Morphological characteristics suggested that each lemur species harbored two different filarial species. Prevalence of microfilarial infection was significantly lower in L. edwardsi than in A. occidentalis. No significant difference in infection intensity between the two host species, and no effect of season, daytime of sampling or sex on prevalence or infection intensity was found. In neither host species, parasite infection showed an influence on body weight as an indicator for body condition.

Conclusions

Our findings support that sleeping site ecology affects ectoparasite infestation in nocturnal, arboreal mammalian hosts in the tropics, whereas there is no significant effect of host sex. The influence of sleeping site ecology to vector-borne hemoparasite risk is less pronounced. The observed parasite infections did not affect body condition and thus may be of minor importance for shaping reproductive fitness. Findings provide first evidence for the specific relevance of sleeping site ecology on parasitism in arboreal and social mammals. Further, our results increase the sparse knowledge on ecological drivers of primate host-parasite interactions and transmission pathways in natural tropical environments.

     

Seasonal population dynamics of the nematode Cystidicoloides tenuissima (Zeder) from the River Swincombe, England

The seasonal population dynamics of adult and larval Cystidicoloides tenuissima were studied in its definitive hosts brown trout, Salmo trutta and juvenile Atlantic salmon, S. salar , and mayfly intermediate host, Leptophlebia marginata , from the River Swincombe, Dartmoor National Park, Devon, U.K. Infective larvae were present in each mayfly generation for almost its entire duration in the steam benthos. The infection parameters (prevalence and mean intensity) and maturation in the fish indicated C. tenuissima was an annual parasite exhibiting a seasonal periodicity and also systematic variation with the host age. Maturation was correlated to river water temperature. Infection parameters increased from September to May, then declined in June and July and remained relatively constant for the rest of the summer. Variation in the fish infection parameters over time, site, and host species appeared to be controlled by transmission related events; the availability of infective larvae, host feeding behaviour and water temperature. The availability of infective larvae and host diet controlled the rate at which parasites were added to the parasite population, but the pattern of gains and losses was determined by a temperature dependent rejection response.     

Detection of a malaria parasite (Plasmodium mexicanum) in ectoparasites (mites and ticks), and possible significance for transmission

Two species of sandflies (Lutzomyia) are competent vectors of Plasmodium mexicanum, a malaria parasite of lizards. The very patchy distribution of sites with high P. mexicanum prevalence in the lizards, and often low or even nil sandfly density at such sites, provoked an evaluation of 2 common lizard ectoparasites, the tick Ixodes pacificus and the mite Geckobiella occidentalis, as potential passive vectors. Plasmodium sp.-specific polymerase chain primers were used to amplify a long segment of the mitochondrial cytochrome b gene that is unlikely to survive intact if the parasite cells are killed within a blood-feeding arthropod. The segment was strongly amplified from sandflies (the positive control for the method) from 1 to 96 hr postfeeding on an infected lizard. For ticks, the gene fragment was poorly amplified at 0 hr postfeed, and not amplified after 2 hr. In contrast, strong amplification of the parasite DNA was observed from mites from 0 to 20 hr postfeed, and weak amplification even at 96 hr.     

Distribution and phylogenetic analyses of an endangered tick,Amblyomma sphenodonti

Abstract

In this study we investigate the geographic distribution, genetic diversity, and phylogenetic relationships of an endangered tick, Amblyomma sphenodonti (Family Ixodidae). Amblyomma sphenodonti and its host, the tuatara (Sphenodon), are found only on small offshore islands around New Zealand. Our results show that Amblyomma sphenodonti has a more severely restricted geographic distribution than its host, as it was found on only eight of 28 islands (four out of 12 island groups) where tuatara still live. The prevalence of A. sphenodonti is likely to have been affected by low host density and fluctuations in host population size as tuatara populations became isolated on offshore islands. Analysis of A. sphenodonti cytochrome oxidase 1 (CO1) sequences indicated a lack of gene flow between islands, with fixed differences in CO1 sequences between islands, but almost no genetic diversity within island populations. A similar phylogenetic pattern to that observed in tuatara mtDNA was observed, indicating co‐evolution of two species, at least since the Pleistocene. Phylogenetic analysis using 18S rRNA sequences suggest that A. sphenodonti is not closely related to other Amblyomma species, and that a separate genus for this species may be warranted. However, data from other ixodid ticks are required before the distinctiveness of A. sphenodonti can be confirmed and the phylogenetic relationships among ixodid ticks fully understood.     

The characteristics of the ixodid tick-vertebrate animal parasitic system]

The parasitic system ixodid tick (parasite)--vertebrate animal (host) is relatively stable in space and time. Equilibrium state in the system is maintained at the low levels of the hosts' infection and moderate intensity of their immunity. Parasite sensitizes the host's organism at the stage of feeding on antigens of its saliva and the host develops different degrees of resistance preventing the subsequent individuals of ticks from normal feeding. Antitick immunity is species specific. Its intensity is defined by the species belonging of the parasite and host, intensity and intervals between infections, availability of "anti-immune mechanisms" in tick and by many other factors, which are realized at the feeding stage. Regulation of the number of ticks, depending on their abundance in the host's population, is attained due to the oversparse, close to negative binomial distribution on hosts. This mechanism functions on the principle of feedback, so that at the excessive number of the parasite some individuals in the host's population, which are especially subjected to infection, do not cope with parasitic burden and die. However, ticks, which failed to finish their feeding and represent a disproportionately great part of the whole parasite's population, die together with them and the parasitic system quickly restores its stability. In anthropocoenoses and ecosystems at different stages of anthropogenic transformation mutual regulation mechanisms of the parasite and host number break down. As a consequence, extremely high rises in the number of ticks and epizootics of agricultural animals associated with them can occur.     

Assessing the Effects of Climate on Host-Parasite Interactions: A Comparative Study of European Birds and Their Parasites

Background

Climate change potentially has important effects on distribution, abundance, transmission and virulence of parasites in wild populations of animals.

Methodology/Principal Finding

Here we analyzed paired information on 89 parasite populations for 24 species of bird hosts some years ago and again in 2010 with an average interval of 10 years. The parasite taxa included protozoa, feather parasites, diptera, ticks, mites and fleas. We investigated whether change in abundance and prevalence of parasites was related to change in body condition, reproduction and population size of hosts. We conducted analyses based on the entire dataset, but also on a restricted dataset with intervals between study years being 5–15 years. Parasite abundance increased over time when restricting the analyses to datasets with an interval of 5–15 years, with no significant effect of changes in temperature at the time of breeding among study sites. Changes in host body condition and clutch size were related to change in temperature between first and second study year. In addition, changes in clutch size, brood size and body condition of hosts were correlated with change in abundance of parasites. Finally, changes in population size of hosts were not significantly related to changes in abundance of parasites or their prevalence.

Conclusions/Significance

Climate change is associated with a general increase in parasite abundance. Variation in laying date depended on locality and was associated with latitude while body condition of hosts was associated with a change in temperature. Because clutch size, brood size and body condition were associated with change in parasitism, these results suggest that parasites, perhaps mediated through the indirect effects of temperature, may affect fecundity and condition of their hosts. The conclusions were particularly in accordance with predictions when the restricted dataset with intervals of 5–15 years was used, suggesting that short intervals may bias findings.     

Further study on Ascogregarina culicis in temperate Argentina: Prevalence and intensity in Aedes aegypti larvae and pupae

The bionomics of South American strains of Ascogregarina spp. are poorly known and the first studies were performed a few years ago. Our main objective was to characterize Ascogregarina culicis population in Aedes aegypti immatures in temperate Argentina. A total of 1800 water-filled containers were inspected within a cemetery of Buenos Aires City through a reproductive period of the host (October 2006-June 2007). The parasite was detected in 16.7% (329/1974) of the immatures and 8.5% (15/177) of the breeding sites. The prevalence decreased from 19.9% in larvae to 6.5% in pupae. In those infected breeding sites, about 85% of the immature mosquitoes harbor the parasite with a median intensity of nine trophozoites per larva and six gametocysts per pupa. The prevalence in shaded containers was higher than in sun exposed ones but the intensity of the infection was quite similar between both lighting conditions. Sun-exposed containers recorded water temperatures significantly higher than those under shade throughout the study period. Parasite trophozoites were only found from January to May with a clear seasonal pattern of prevalence. Monthly values of parasite prevalence and mosquito host (percentage of breeding sites and number of immatures) were significantly correlated at p < 0.05 when a temporal delay of two months was considered. Our results suggest that parasite prevalence is spatially and temporally heterogeneous in temperate urban Argentina, and these variations are associated with the host abundance.     

New ruminant hosts and wider geographic range identified for Babesia odocoilei (Emerson and Wright 1970)

Babesia odocoilei was found to infect two previously unknown host species, desert bighorn sheep (Ovis canadensis nelsoni) and musk oxen (Ovibos moschatus), both of which are members of the family Bovidae. Previously, B. odocoilei has been reported in only Cervidae hosts. New geographic regions where B. odocoilei infections have not been reported previously include Pennsylvania and New York, where fatal babesiosis has occurred in reindeer (Rangifer tarandus tarandus); New Hampshire, where elk (Cervus elaphus canadensis) have been affected; and California, home of the infected desert bighorn sheep. Infection with B. odocoilei in these hosts was confirmed by parasite small subunit ribosomal RNA gene sequence analysis. A serosurvey for B. odocoilei antibody activity in New Hampshire showed prevalence rates of 100% at two elk farms and 12% at another farm. Control of potential vector ticks, Ixodes scapularis, especially when translocating livestock, is imperative to prevent outbreaks of babesiosis in managed herds of potential host species.