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It was assessed the parasitic relationship between by 2 morphospecies of microphallid metacercariae and their second intermediate host, the amphipod Apohyale hirtipalma with the body length and sex of the hosts, and the abundance of shore birds (definitive hosts). Amphipod mortality induced by the parasites was assessed through the relationship between the variance/mean parasite abundance ratio with host body length for each metacercariae morphospecies. Four sites at the Biobío Region (36°S), Chile, were selected because of contrasting abundance of potential definitive hosts (Aves: Laridae), from where 240 amphipods were collected from intertidal pools (60 in each sampling locality). Total prevalence was 57.5% and metacercariae found, belonged to 2 unidentified morphospecies of microphallid subfamilies (Microphallinae, 28.3% and Maritrematinae, 36.7%). The prevalence and abundance of metacercariae increased with the amphipod body, although their variations were associated to the abundance of shorebirds. The prevalence of Microphallinae did not have differences among sexes in their relationship with the host body length, while among Maritrematinae, male amphipods showed higher prevalence than females of similar body length. It was also determined that Maritrematinae would cause more mortality than Microphallinae. Local variations of the abundance of other hosts involved in the microphallid life cycles as well as of prevailing local environmental conditions and amphipod behavior may be keys for a better understanding of the abundance and prevalence variations of these parasites., Se evaluó la relación parasítica por 2 morfoespecies de metacercarias (Microphallidae) en su segundo hospedador intermediario, el anfípodo Apohyale hirtipalma según el largo corporal y sexo del anfípodo, y la abundancia de aves costeras (hospedadores definitivos). La mortalidad de anfípodos parasitados fue evaluada a través de la relación varianza/promedio de la abundancia de cada morfoespecie de metacercaria con el tamaño corporal de los anfípodos. Cuatro localidades de muestreo fueron seleccionadas en la región del Biobío (36°S), Chile, con diferencias contrastantes en la abundancia de hospedadores definitivos (Aves: Laridae). Se recolectaron 240 anfípodos desde pozas intermareales (60 en cada localidad de muestreo). La prevalencia total de metacercarias fue de 57,5%, detectándose metacercarias de 2 subfamilias de Microphallidae (Microphallinae 28,3% y Maritrematinae 36,7%), aun no identificadas a un nivel taxonómico más bajo. La prevalencia de ambas morfoespecies de metacercarias aumentaba con la longitud total de los anfípodos, aunque gran parte de sus variaciones estuvieron asociadas a la abundancia de aves costeras. La prevalencia de Microphallinae fue similar entre sexos en la relación al tamaño del cuerpo del hospedador, mientras que en los anfípodos machos parasitados con Maritrematinae mostraron mayor prevalencia que las hembras de similar tamaño corporal. Se determinó además que metacercarias Maritrematinae ocasionarían mayor mortalidad de anfípodos que Microphallinae. Las variaciones locales de abundancia de otros hospedadores involucrados en el ciclo de vida de estos digeneos, como también las condiciones ambientales locales y la conducta de los anfípodos, serían claves para comprender las variaciones de prevalencia y abundancia de estos parásitos.

[Background]: Parasites play pivotal roles in host population dynamics and can have strong ecological impacts on hosts. Knowledge of the effects of parasites on hosts is often limited by the general observation of a fraction of individuals (mostly adults) within a population. The aim of this study was to assess the prevalence of malaria parasites in adult (≥1 year old) and nestling (7-11 day old) Tawny pipits Anthus campestris, to evaluate the influence of the host sex on parasite prevalence in both groups of age, and explore the association between infections and body condition (adults) and growth (nestlings). [Methods]: Two hundred Tawny pipits (105 adults and 95 nestlings) from one Spanish population were screened for avian malaria parasites (Haemoproteus and Plasmodium) using the polymerase chain reaction (PCR)-based methods. Body condition (body mass against a linear measure of size) was measured in adults and growth rate (daily mass gain) was calculated for nestlings. [Results]: The overall prevalence of infection was 46 %. Sixteen different mitochondrial cytochrome b haplotypes of Plasmodium spp. and one Haemoproteus spp. haplotype were found. Malaria parasites were equally prevalent in nestlings and adults (45 and 46 %, respectively). Males were more likely to be infected by parasites than females, and this sex-bias parasitism was evident in both adults and nestlings. Furthermore, a lower daily mass gain during nestling growth in males than in females following infections were found, whereas the effect of infections on body condition of adults was detrimental for females but not for males. [Conclusions]: Age-specific differences in physiological trade-offs and ecological factors, such as nest predation would explain, at least in part, the observed host sex and age-related patterns in Tawny pipits.

Globally small mammals are important hosts of ectoparasite vectors of pathogens of medical, veterinary and economic importance. Insectivores are currently understudied as hosts of pathogen vectors. However, data are needed on the diversity of such vectors before we can investigate the underlying factors affecting ectoparasite distribution. Abiotic (e.g. temperature and rainfall) and biotic (e.g. host sex) factors have been identified as the main determinants of host–parasite interactions. The present study describes the ectoparasite community of insectivorous eastern rock sengis (Elephantulus myurus) in a nature reserve in the Gauteng province, South Africa, and how it varies with season and host sex. A total of 81 sengis were examined for the presence of ticks, mites, fleas and lice between April 2010 and April 2011. The ectoparasite assemblage comprised 11 groups of tick species, a single mite family, one louse and two flea species, with ticks and mites being the most numerous ectoparasites recovered. The prevalence and/or abundance of two commonly collected ticks (Ixodes spp. and Rhipicephalus warburtoni/arnoldi) and chigger varied with season. In addition, female-biased tick burdens were apparent for one ectoparasite species possibly due to reproductive investment. The mechanisms causing the observed patterns should be addressed in future studies

Globally small mammals are important hosts of ectoparasite vectors of pathogens of medical, veterinary and economic importance. Insectivores are currently understudied as hosts of pathogen vectors. However, data are needed on the diversity of such vectors before we can investigate the underlying factors affecting ectoparasite distribution. Abiotic (e.g. temperature and rainfall) and biotic (e.g. host sex) factors have been identified as the main determinants of host–parasite interactions. The present study describes the ectoparasite community of insectivorous eastern rock sengis (Elephantulus myurus) in a nature reserve in the Gauteng province, South Africa, and how it varies with season and host sex. A total of 81 sengis were examined for the presence of ticks, mites, fleas and lice between April 2010 and April 2011. The ectoparasite assemblage comprised 11 groups of tick species, a single mite family, one louse and two flea species, with ticks and mites being the most numerous ectoparasites recovered. The prevalence and/or abundance of two commonly collected ticks (Ixodes spp. and Rhipicephalus warburtoni/arnoldi) and chigger varied with season. In addition, female-biased tick burdens were apparent for one ectoparasite species possibly due to reproductive investment. The mechanisms causing the observed patterns should be addressed in future studies

Individuals often differ in their ability to transmit disease and identifying key individuals for transmission is a major issue in epidemiology. Male hosts are often thought to be more important than females for parasite transmission and persistence. However, the role of infectious females, particularly the transient immunity provided to offspring through maternal antibodies (MatAbs), has been neglected in discussions about sex-biased infection transmission. We examined the effect of host sex upon infection dynamics of zoonotic Puumala hantavirus (PUUV) in semi-natural, experimental populations of bank vole (Myodes glareolus). Populations were founded with either females or males that were infected with PUUV, whereas the other sex was immunized against PUUV infection. The likelihood of the next generation being infected was lower when the infected founders were females, underlying the putative importance of adult males in PUUV transmission and persistence in host populations. However, we show that this effect probably results from transient immunity that infected females provide to their offspring, rather than any sex-biased transmission efficiency per se. Our study proposes a potential contrasting nature of female and male hosts in the transmission dynamics of hantaviruses.