Helminth parasitism in two closely related South African rodents: abundance, prevalence, species richness and impinging factors

Nestedness and beta diversity of gastrointestinal helminth communities in common warthogs, Phacochoerus africanus (Suidae), at 2 localities in South Africa

Few studies have investigated the ecological interactions between wild species of Suidae and their parasites, leaving our knowledge concerning this host–parasite system fragmented. In the present study, we applied network studies to analyse community nestedness in helminth assemblages of common warthogs, Phacochoerus africanus (Gmelin) (Suidae). Helminth data were compiled from 95 warthogs, including young and adult males and females, from 2 different conservation areas in Mpumalanga and Limpopo Provinces, South Africa, collected monthly over a period of 1 year each. The aim was to study the effect of host sex, age and season of sampling on the structure of helminth infracommunities harboured by the warthogs and to search for non-random structural patterns in the warthog–helminth interaction networks. Furthermore, we investigated the influence of a warthog's age, sex and season of sampling on beta diversity and dark diversity of their helminth infracommunities. Lastly, we asked whether the effects of host sex, age and sampling season on helminth communities differed between the 2 localities. We found that helminth communities of warthogs were nested and host–parasite interactions were influenced by all 3 factors as well as combinations thereof. However, the resulting patterns differed at the 2 localities, indicating that local environmental processes are important drivers of community structure.

Epidemiological, clinical and pathological aspects of lethal acanthocephalosis in captive neotropical primates

BACKGROUND

Acanthocephalosis is an important cause of death in captive New World primates (NWP). Once established in a colony, it is extremely difficult to treat and control, quickly spreading among NWP with a high mortality rate. This study aimed to characterize the disease associated with infection with acanthocephalans according to its epidemiological, clinical, and anatomopathological aspects in a captive NWP population.

METHODS

From 2010 to 2020, a Brazilian zoo had recurrent deaths of NWP associated to acanthocephalan parasitism. Clinical and pathological profiles of these animals were analyzed considering the host species, sex, age, weight, clinical signs, therapeutic protocols, and pathological findings.

RESULTS

A total of 27 deaths associated with acanthocephalosis were recorded, all lethal cases affected tamarins and lion tamarins, corresponding to 67.5% of total deaths during the course of this study. Ten animals died with no previously detected clinical signs, whereas cases with noticeable clinical signs often had apathy and progressive weight loss, resulting in cachexia. Symptomatic NWP were treated with anthelmintic protocols, antibiotics, and support therapy. However, all hospitalized animals died and had grossly detectable adult acanthocephalans in the intestinal lumen that were identified as Prosthenorchis sp., which were associated with transmural and ulcerative enteritis.

CONCLUSIONS

This report revealed the impact of acanthocephalosis in a naturally infected captive colony of NWP, particularly affecting tamarins (Saguinus spp.) and lion tamarins (Leontopithecus spp.), with failed treatment and control strategies.

Linking Behavior, Co-infection Patterns, and Viral Infection Risk With the Whole Gastrointestinal Helminth Community Structure in Mastomys natalensis

Infection probability, load, and community structure of helminths varies strongly between and within animal populations. This can be ascribed to environmental stochasticity or due to individual characteristics of the host such as their age or sex. Other, but understudied, factors are the hosts' behavior and co-infection patterns. In this study, we used the multimammate mouse (Mastomys natalensis) as a model system to investigate how the hosts' sex, age, exploration behavior, and viral infection history affects their infection risk, parasitic load, and community structure of gastrointestinal helminths. We hypothesized that the hosts' exploration behavior would play a key role in the risk for infection by different gastrointestinal helminths, whereby highly explorative individuals would have a higher infection risk leading to a wider diversity of helminths and a larger load compared to less explorative individuals. Fieldwork was performed in Morogoro, Tanzania, where we trapped a total of 214 individual mice. Their exploratory behavior was characterized using a hole-board test after which we collected the helminths inside their gastrointestinal tract. During our study, we found helminths belonging to eight different genera: Hymenolepis sp., Protospirura muricola, Syphacia sp., Trichuris mastomysi, Gongylonema sp., Pterygodermatites sp., Raillietina sp., and Inermicapsifer sp. and one family: Trichostrongylidae. Hierarchical modeling of species communities (HMSC) was used to investigate the effect of the different host-related factors on the infection probability, parasite load, and community structure of these helminths. Our results show that species richness was higher in adults and in females compared to juveniles and males, respectively. Contrary to our expectations, we found that less explorative individuals had higher infection probability with different helminths resulting in a higher diversity, which could be due to a higher exposure rate to these helminths and/or behavioral modification due to the infection.

Angiostrongylus cantonensis in urban populations of terrestrial gastropods and rats in an impoverished region of Brazil

The nematode Angiostrongylus cantonensis is the most common cause of neuroangiostrongyliasis (manifested as eosinophilic meningitis) in humans. Gastropod molluscs are used as intermediate hosts and rats of various species are definitive hosts of this parasite. In this study, we identified several environmental factors associated with the presence and abundance of terrestrial gastropods in an impoverished urban region in Brazil. We also found that body condition, age and presence of co-infection with other parasite species in urban Rattus norvegicus, as well as environmental factors were associated with the probability and intensity of A. cantonensis infection. The study area was also found to have a moderate prevalence of the nematode in rodents (33% of 168 individuals). Eight species of molluscs (577 individuals) were identified, four of which were positive for A. cantonensis. Our study indicates that the environmental conditions of poor urban areas (presence of running and standing water, sewage, humidity and accumulated rain and accumulation of construction materials) influenced both the distribution and abundance of terrestrial gastropods, as well as infected rats, contributing to the maintenance of the A. cantonensis transmission cycle in the area. Besides neuroangiostrongyliasis, the presence of these hosts may also contribute to susceptibility to other zoonoses.

Parasite counts or parasite incidences? Testing differences with four analyses of infracommunity modelling for seven parasite-host associations

One of the challenges in studies of parasite community ecology is whether the input data for analyses should be parasite abundances/counts, i.e. count data (CD), or parasite incidences (presences/absences), i.e. incidence data (ID). We analysed species responses to environmental factors and species associations in the infracommunities of helminths and ectoparasites in four hosts from Europe (Sorex araneus and Myodes glareolus) and South Africa (Rhabdomys pumilio and Rhabdomys dilectus) and compared the results of four analyses [redundancy analysis (RD), RLQ analysis, joint species distribution modelling (JSDM) and Markov random fields (MRF)] that used either CD or ID as an input. In addition, we compared the differences between the CD and ID results of two analyses (JSDM and MRF) across parasite species between (a) host species within helminths and ectoparasites; (b) helminths and ectoparasites within a host species; and (c) parasite species with contrasting levels of intensity. The results of most analyses for the majority of parasite-host associations were qualitatively similar. However, models based on the ID input performed better than models based on the CD input in three out of four types of analyses (RDA, JSDM and MRF). The differences between the CD and ID models varied between host species (being the lowest in R. pumilio for JSDM and in S. araneus for MRF). However, they were not affected by the level of parasite intensity.

Functional and phylogenetic uniqueness of helminth and flea assemblages of two South African rodents

The loss of a particular species from a community may have different effects on its functioning, depending on the presence or absence of functionally similar or phylogenetically close species in that community (redundancy). Redundancy is thus defined as the fraction of species diversity not expressed by functional or phylogenetic diversity. We assessed functional and phylogenetic alpha- and beta-redundancy in helminth and flea assemblages of two species of South African rodents, Rhabdomys dilectus and Rhabdomys pumilio, using community uniqueness as the inverse indicator of redundancy. We asked whether patterns of functional and phylogenetic alpha- and beta-uniqueness differed between (i) parasite groups (endo- versus ectoparasites), (ii) host species within parasite groups, and (iii) biomes within host species. We found differences between the two hosts in the functional and phylogenetic alpha-uniqueness (but not beta-uniqueness) of flea, but not helminth, assemblages. Significant correlations between the alpha-uniqueness of parasite assemblages and the total parasite prevalence were found only for phylogenetic uniqueness and only in helminths. Pairwise site-by-site dissimilarities in uniqueness (beta-uniqueness) and pairwise dissimilarity in prevalence were significantly associated (positively) in helminths but not in fleas. A between-biome difference in functional (but not phylogenetic) alpha-uniqueness was found in both helminth and flea assemblages harboured by R. pumilio. We conclude that the resilience of parasite assemblages in terms of the effect on hosts depends not only on their transmission strategy but also on traits of host species and environmental factors.

Phylogenetics and genetic variation of Heligmosomoides thomomyos in Western pocket gophers (Thomomys spp.)

The host specificities and systematics of North American Heligmosomoides species remain particularly uncertain. The primary aim of this study was to verify that a species described previously based only on morphology, H. thomomyos, from pocket gopher (Rodentia: Geomyidae) hosts in Oregon represented a monophyletic lineage. In order to address this aspect, as well as to further understand relationships and geographic patterns, we carried out phylogenetic, genetic diversity, and population dynamic analyses using partial 18S rRNA and COI mtDNA sequences of Heligmosomoides specimens. Phylogenetic analyses suggested that there are likely multiple Heligmosomoides species present in these hosts. This was supported by the high degree of divergence and differentiation found among populations, significant population structure between locations, and a modest positive association between geographic and genetic distances. This study serves as the first molecular characterization and first phylogenetic report of H. thomomyos, and documents two new host records for this parasite. The relationship of H. thomomyos among pocket gopher hosts and to other Heligmosomoides species, however, warrants continued study.

Effects of latitude, host body size, and host trophic guild on patterns of diversity of helminths associated with humans, wild and domestic mammals of Mexico

Parasites are strictly associated with their hosts and present a great diversity of life histories, often resulting in different diversity patterns than those observed in free-living species. However, ecological approaches have detected that, in some cases, mammal-associated helminths respond similarly to non-parasitic species in terms of diversity patterns. Using 2200 recorded interactions, we analysed the diversity patterns of helminths (Acanthocephala, Nematoda and Platyhelminthes) harbored by humans, wild and domestic mammals of Mexico, depending on latitude, host body mass and trophic guild (carnivore, herbivore, insectivore, omnivore), considering helminth richness and average taxonomic distinctness, and host phylogenetic diversity and phylogenetic clustering. Latitude was positively correlated with the average taxonomic distinctness encompassing the three parasite phyla and nematodes. Northern latitudes had less taxonomically related parasite assemblages. Host body mass had a significant negative relationship with the average taxonomic distinctness of acanthocephalans and the richness of helminths associated to wild hosts. The omnivore hosts had greater parasite richness, while insectivores had a less taxonomically related parasite assemblage and herbivores had a more heterogeneous parasite assemblage. Our results highlight the importance of incorporating different dimensions of diversity, such as average taxonomic distinctness and to consider the composition of parasite assemblages to better understand their diversity patterns.

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Four diversity measures were used to describe diversity patterns of helminths.

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Latitude was positively correlated with helminth average taxonomic distinctness.

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Host body mass was negatively related with the helminth richness of wildlife hosts.

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Helminth sets of omnivore hosts were richer in parasite species.

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Helminth sets of insectivore hosts had a wider taxonomic breadth.

Nematodes and cestodes of rodents in South Africa: baseline data on diversity and geographic distribution

Currently, descriptive information on the host range and geographic distribution of helminth parasites associated with naturally occurring rodents in South and southern Africa is scant. Therefore, we embarked on a countrywide study to: (1) identify gastrointestinal helminths and their host range, and (2) provide baseline data on the geographic distribution of helminths across the country. Altogether, 55 helminth taxa were recovered from at least 13 rodent species (n = 1030) at 26 localities across South Africa. The helminth taxa represented 25 genera (15 nematodes, nine cestodes and one acanthocephalan). Monoxenous nematodes were the most abundant and prevalent group, while the occurrence of heteroxenous nematodes and cestodes was generally lower. The study recorded several novel helminth-host associations. Single-host-species infections were common, although multiple-host-species infections by helminth species were also recorded. Monoxenous nematodes and some cestodes were recovered countrywide, whereas heteroxenous nematodes were restricted to the eastern regions of South Africa. The study highlights the as yet unexplored diversity of helminth species associated with naturally occurring rodent species and provides initial data on their geographical distribution in South Africa.

Beta diversity of gastrointestinal helminths in two closely related South African rodents: species and site contributions

A fundamental aim of parasite ecology is to understand the mechanisms behind spatial variation in diversity and structure of parasite assemblages. To understand the contribution of individual parasite species and their assemblages to spatial variation in parasite communities, we examined species contributions to beta diversity (SCBD) and local contributions to beta diversity (LCBD) of parasitic gastrointestinal helminths (nematodes and cestodes) in two closely related rodents, Rhabdomys dilectus and Rhabdomys pumilio, from 20 localities across South Africa. Although the two Rhabdomys spp. are morphologically similar, they differ substantially in body size, habitat preference, and sociality. We asked whether the variation in life history traits and infection parameters are associated with SCBD of helminths and whether variation in environmental factors, host population density, and species richness of host communities are associated with LCBD of component assemblages of helminths. We also considered spatial factors to test whether LCBD of helminth assemblages demonstrate geographic structure. We found that the contribution of helminth species parasitic in both hosts to beta diversity significantly increased with characteristic prevalence of these species, whereas mean abundance, type of life cycle, and location in the host's gut had no effect on SCBD. The LCBD of helminth assemblages showed a significant positive correlation with environmental factors in both host species. Our results suggest that predictors of variation in SCBD and LCBD may substantially differ between parasites with different infection parameters and/or parasite communities at different hierarchical scales.

Variation in the prevalence and abundance of acanthocephalans in brown-nosed coatis Nasua nasua and crab-eating foxes Cerdocyon thous in the Brazilian Pantanal

Host infection by parasites is influenced by an array of factors, including host and environmental features. We investigated the relationship between host sex, body size and age, as well as seasonality on infection patterns by acanthocephalan in coatis (Procyonidae: Nasua nasua) and in crab-eating foxes (Canidae: Cerdocyon thous ) from the Brazilian Pantanal wetlands. Between 2006 and 2009, we collected faecal samples from these hosts and analyzed for the presence of acanthocephalan eggs. Prevalence, abundance and intensity of eggs of acanthocephalans were calculated. Egg abundance was analyzed using generalized linear models (GLM) with a negative binomial distribution and models were compared by Akaike criteria to verify the effect of biotic and abiotic factors. Prevalence of acanthocephalans was higher in the wet season in both host species but did not differ between host sexes; however, adult crab-eating foxes showed higher prevalence of acanthocephalan eggs than juveniles. In contrast, prevalence of acanthocephalan eggs found in coatis was higher in coati juveniles than in adults. Host age, season and maximum temperature were the top predictors of abundance of acanthocephalan eggs in crab-eating foxes whereas season and host sex were predictors of egg abundance in coatis. The importance of seasonality for abundance of acanthocephalan was clear for both host species. The influence of host-related attributes, however, varied by host species, with host gender and host age being important factors associated with prevalence and parasite loads.

Long-term spatiotemporal stability and dynamic changes in helminth infracommunities of spiny mice (Acomys dimidiatus) in St. Katherine's Protectorate, Sinai, Egypt

The importance of parasites as a selective force in host evolution is a topic of current interest. However, short-term ecological studies of host–parasite systems, on which such studies are usually based, provide only snap-shots of what may be dynamic systems. We report here on four surveys, carried out over a period of 12 years, of helminths of spiny mice (Acomys dimidiatus), the numerically dominant rodents inhabiting dry montane wadis in the Sinai Peninsula. With host age (age-dependent effects on prevalence and abundance were prominent) and sex (female bias in abundance in helminth diversity and in several taxa including Cestoda) taken into consideration, we focus on the relative importance of temporal and spatial effects on helminth infracommunities. We show that site of capture is the major determinant of prevalence and abundance of species (and higher taxa) contributing to helminth community structure, the only exceptions beingStreptopharausspp. andDentostomella kuntzi.We provide evidence that most (notably the Spiruroidea,Protospirura muricola,Mastophorus murisandGongylonema aegypti, but with exceptions among the Oxyuroidae, e.g.Syphacia minuta), show elements of temporal-site stability, with a rank order of measures among sites remaining similar over successive surveys. Hence, there are some elements of predictability in these systems.

Intra- and interspecific similarity in species composition of helminth communities in two closely-related rodents from South Africa

To reveal factors responsible for spatial variation in parasite community composition we studied patterns of similarity in helminth species composition in two closely-related rodents (Rhabdomys pumilioandRhabdomys dilectus) that differ in their social and spatial behaviour and live under different environmental conditions across 20 localities in South Africa. We asked whether the two hosts harbour similar assemblages, whether these are more dissimilar between than within hosts and if host social structure, behaviour or environment affects similarity patterns in helminth infracommunities within and among localities. We also investigated whether similarity in species composition of helminth component communities decreases with an increase of geographic distance between host populations. We found that the pattern of space use by the hosts rather than their social behaviour promotes differences in helminth species composition between host species as well as among host populations from different localities. The rate of distance decay of similarity in species composition of helminth component communities differed between the two hosts due to difference in the degree of environmental variation across their geographic ranges. We conclude that patterns of spatial variation in helminth species composition are driven mainly by host spatial behaviour and, to a lesser extent, by environment-associated factors.