Helminth community structure in two species of arctic-breeding waterfowl

Ecto- and endoparasites of common reedbuck, Redunca arundinum, at 2 localities in KwaZulu-Natal Province, South Africa: community and network structure

Parasite community structure is governed by functional traits of hosts and parasites. Notably, parasite populations and communities respond to host social and spatial behaviour. Many studies demonstrating these effects dealt with small-bodied host species, while the influence of host social patterns on parasite communities in large hosts remains understudied. In an earlier study on nyalas (Tragelaphus angasii), host age was more important than sex in structuring helminth communities and networks, but the influence of both was mediated by local environmental conditions, creating different locality patterns. Common reedbuck (Redunca arundinum) differ from nyalas in spatial and social behaviour. Based on helminth and ectoparasite data from 56 reedbuck examined at 2 localities in KwaZulu-Natal Province, we asked which patterns are similar and which differ between the 2 host species. Similar to nyalas, reedbuck age was more important than sex in structuring communities and networks. However, local environmental conditions exerted the strongest influence on transmission patterns, especially in ectoparasites. Complex interactions between reedbuck traits, parasite traits and local environmental conditions modulated the risk of infection differently at the 2 sites, confirming our earlier findings in nyalas that pooling data from different locations may obscure location-specific parasite community patterns. Similarities between patterns in reedbuck and nyalas, despite their behavioural differences, suggest some common patterns in parasite community ecology that, in turn, are determined mostly by parasite traits and population dynamics.

The first record of Heterakis gallinarum as a cause of fatal nodular typhlitis in golden pheasants (Chrysolophus pictus) in India

Background

Heterakidosis is one of the most prevalent parasitic diseases in birds, the caecae of a variety of wild and domestic birds are infected with these nematodes. In pheasants, nodular typhlitis is a lethal disease caused mainly by infection with Heterakis isolonche alone or in conjunction with Heterakis gallinarum. H. gallinarum has long been recognized to infect birds with low pathogenicity, with only a few fatal cases previously reported.

Case description

This paper describes a case of fatal nodular typhlitis due to H. gallinarum in a male and female pair of adult golden pheasants (Chrysolophus pictus) from a zoological garden in Uttar Pradesh, India.

Findings/treatment and outcome

The caecum had multiple serosal and mucosal nodules, the majority of which were found to contain various stages of parasites embedded in the center along with the free forms in the caecal contents. Histopathologically, these nodules were generally represented by granulomas centered on necrotic parasite debris, with the occasional reactive fibrous hyperplastic tissue reaction. Based on the morphology and nematode-specific internal transcribed spacer (ITS) ITS1-5.8 rRNA-ITS2 region-based PCR, the nematode was identified as H. gallinarum. The presence of H. gallinarum was further confirmed by sequencing the ITS region followed by phylogenetic analysis. According to the author's best knowledge, this is the first instance of H. gallinarum being linked to nodular typhlitis in pheasants in India.

Conclusion

Our findings confirm that H. gallinarum, other than H. isolonche, can induce severe nodular typhlitis with a fatal outcome in pheasants.

Impact of host sex and age on the diversity of endoparasites and structure of individual-based host-parasite networks in nyalas (Tragelaphus angasii Angas) from three game reserves in KwaZulu-Natal province, South Africa

In recent years, numerous studies have examined the effect of host sex and age on the structure of parasite communities in several host taxa under various environmental conditions and in different geographic regions. However, the influence of such factors on the structure of host-parasite networks has received less attention, and remarkably few studies have been carried out on large terrestrial mammals. In this study, we investigated the effects of host age and sex on the parasite infra- and component communities of nyalas (Tragelaphus angasii) and on the structure of individual-based nyala-endoparasite networks. We also aimed to evaluate to what extent these effects vary spatially and if they are mediated by conservation management. Based on a data set of internal macroparasites of 74 nyalas from three game reserves in KwaZulu-Natal province, we found that host age strongly influenced parasite community structure as well as the structure of parasite-nyala networks, whereas host sex played a minor role. However, the effects of both host sex and age were mediated by environmental conditions and thus led to different patterns at the three localities. Our findings highlight that host-parasite communities from different localities should not be pooled when conducting host-parasite network and community studies as this may bias results and mask patterns that are typical for a given locality.

Epidemiological Studies on Nematode Parasites of Domestic Geese (Anser anser f. domesticus) and First Molecular Identification and Phylogenetic Analysis of Heterakis dispar (Schrank, 1790) in Egypt

PURPOSE

Gastrointestinal nematodes are one of the most important constraints of poor geese health and productivity, in addition to being involved in great economic losses for various poultry sectors. This study primarily aimed at determining the epidemiological profile and risk factors associated with the occurrence of gastrointestinal (GI) nematode parasites in geese in Egypt. The phylogenetic relationships between heterakids were the second aim.

METHODS

For achieving these aims, a total 180 of intestinal samples were screened for the presence of gastrointestinal nematodes over a period of one year from December 2018 to November 2019. Furthermore, A PCR-based DNA sequencing of the mitochondrial NADH dehydrogenase subunit1 gene (nad1) was conducted for characterization of adult Heterakis dispar.

RESULTS

The current search revealed that the overall prevalence was 33.33% (60/180). Five species of nematode species was encountered in this study, namely Capillaria spp., Heterakis gallinarum (Schrank, 1788), Ascaridia galli (Schrank, 1788), Subulura brumpti (Lopez-Neyra, 1922) and Heterakis dispar (Schrank, 1790). A positive relationship was found between the prevalence of nematode infection and age of tested geese revealing that the high prevalence was found in adults rather than young birds (P = 0.03). Moreover, there was no significant difference in the prevalence of nematode infection between male and female geese (P > 0.05). Also, there was strong significant seasonal trends in the prevalence of the recovered helminths with the maximum infection was observed in summer season and lowest in winter (P = 0.002). The BLAST analysis of H. dispar nad1 sequence showed a 96.4% similarity with the sequences of H. dispar Heilongjiang. It also showed a lower similarity to the mitochondrial gene sequences of H. gallinarum (84.4%). This is the first molecular identification and report of genetic diversity of Heterakis dispar in geese from Egypt.

CONCLUSIONS

The current finding initially provides a concise account of knowledge about the epidemiology of gastrointestinal nematodes infecting geese and are considered as a starting point for the implementation of appropriate control and prophylactic schemes for GIT nematodiasis. It also confirms the potential uses of genetic techniques for taxonomic studies of different parasites.

Prevalence of Heterakis Infection in Parental Flocks of Geese

The prevalence of Heterakis infection in reproductive geese from 56 flocks was investigated between February 2015 and November 2019 by using both anatomopathologic and coproscopic examinations. The nematodes were microscopically examined, and 37.5% (21/56) of the flocks were infected with Heterakis nematodes, mostly with Heterakis dispar (35.7%). In one particular flock, a Heterakis gallinarum infection was noted. In two flocks, Heterakis infection was identified only during coproscopic examination. The infection susceptibility of the geese depended on the bird's age-in the first reproductive season, 50% of the flocks were positive; in the second season, 42% were positive; and in the third season, 30% were positive. The number of nematodes in each necropsied goose varied from 8 to 216 individuals. During the 5 years of epidemiologic analysis, the infection occurrence decreased from 66.7% to 11%.

Gastrointestinal nematodes in two galliform birds from South Africa: patterns associated with host sex and age

Parasite ecology has recently focused on elucidating patterns and processes that shape helminth communities in avian hosts. However, helminths parasitizing gamebirds are still poorly understood. Here we describe the gastrointestinal nematode fauna of Swainson's spurfowl, Pternistis swainsonii (Phasianidae) and helmeted guineafowl, Numida meleagris (Numididae), collected at three and four localities, respectively, in South Africa and analyze the prevalence, mean abundance and diversity of their helminth communities. Eleven nematode species were collected from spurfowl, which had a mean number of nematode species per host of 3.01 ± 0.18, whereas guineafowl harboured 15 nematode species, with a mean number of nematode species per host of 3.93 ± 0.12. Focusing on the most prevalent species, we also asked if host sex and/or age were associated with infracommunity structure with regard to nematode counts and species richness, as well as the species and taxonomic composition of infracommunities. While pooling data of nematode species masked the influence of host characteristics on helminth communities, analysis of individual nematode species revealed a number of patterns. In particular, adult female bias was seen in Tetrameres swainsonii in spurfowl and in Allodapa dentigera and Gongylonema congolense in guineafowl; Acuaria gruveli reached higher numbers in adult spurfowl than in juveniles, and helminth infracommunities in juvenile male guineafowl were more species rich than those in adult males. Combined, our results suggest that helminth communities of spurfowl and guineafowl are associated with a complex interplay of numerous factors, including host characteristics, parasite traits and environmental conditions.

Molecular Identification and Phylogenetic Analysis of Heterakis dispar Isolated from Geese

Purpose

Heterakidosis is a common parasitic infection caused in domestic birds by Heterakis species: Heterakis gallinarum, H. isolonche, and H. dispar. Among them, the best described species is H. gallinarum, noted mainly in gallinaceous birds. In waterfowl, H. dispar is the predominant species. The variations in morphology and host specificity qualify H. dispar as a different species, but the phylogenetic relationships between heterakids were unclear for a long time, because of a lack of H. dispar sequences.

Methods

The authors provided the molecular data for H. dispar and analyzed the obtained sequences of the partial 18S rRNA gene and region ITS1-5.8SrRNA-ITS2 with the homological sequences.

Results

The 18S rRNA PCR product of H. dispar was about 800 bp, and the ITS-5.8S-ITS2 PCR product was about 920 bp, noticeably smaller size compared to H. gallinarum product. The BLAST analysis of H. dispar 18S sequence showed a 99% similarity with the sequences of Heterakis gallinarum and Ascaridia galli, 98% with A. nymphii, but only 94% with the sequence of Heterakis sp. Our ITS sequence of H. dispar was almost identical to the H. isolonche isolate, there is only one nucleotide of difference among the 943 sites analyzed. It also showed a lower similarity to the ITS sequences of H. gallinarum (88%), H. spumosa (87%), and H. dahomensis (87%).

Conclusions

In our phylogenetic analysis, it is the first attempt at the reconstruction of relationships within this superfamily Heterakoidea based on 18S rDNA and ITS region.