Assessment of the helminth fauna in northern bobwhites (Colinus virginianus) occurring within South Texas

Abstract

Populations of northern bobwhites (Colinus virginianus; hereafter bobwhite) have been declining across their geographic range in North America, prompting consideration of the role parasites may play. We conducted this study to learn about the helminth fauna in South Texas, a region that supports a sustainable bobwhite population. Helminths were examined from 356 bobwhites collected during the 2014–2015 (n = 124) and 2015–2016 (n = 232) hunting seasons, when increasing trends in precipitation were observed in comparison with the previous two years. Ten helminth species were found, consisting of 14,127 individuals. Of these, all are heteroxenous parasites and three are pathogenic (Dispharynx nasuta, Tetrameres pattersoni and Oxyspirura petrowi). Aulonocephalus pennula numerically dominated the component community (81% prevalence, 99% of the total helminths found), whereas each of the remaining species occurred rarely (≤9% prevalence) and contributed few individuals (≤0.4%) to the helminth community. Prevalence and abundance of A. pennula were not influenced by host age, sex or body mass, but abundance was higher during the 2014–2015 than the 2015–2016 hunting season. Our findings indicate that the helminth community in bobwhites from South Texas can vary during long-term, highly variable precipitation conditions and these communities are more similar to those found in the Rolling Plains of Texas than those found in the eastern part of the bobwhite's geographic range in the US.

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

“…There was no variation between the sexes and ages of spurfowl in counts of A. suctoria. Similarly, previous authors reported an absence of differences in A. pennula infections across host age, sex and mass in northern bobwhites (Bruno et al 2019;Shea et al 2021). Both A. suctoria and A. pennula demonstrated the highest prevalence and were the numerically dominant species in their respective hosts.…”

“…This relatively fast accumulation of helminth species and numbers in the early phase of juvenile development might also explain why some studies obtained different results for the influence of host age on a given nematode species in the same host species. Olsen and Fedynich (2016) reported a higher prevalence and abundance of the subulurid Aulonocephalus pennula (Canavan, 1929) in adult than in juvenile northern bobwhites, while this did not differ in northern bobwhites from the same area collected during a later study (Shea et al 2021). However, fluctuating environmental conditions at the time of collection, influencing survival of free-living infective stages and abundance of arthropod intermediate hosts, might also have caused these differences (Crowe 2000;Calvete et al 2004;Olsen and Fedynich 2016).…”

“…In contrast, higher infection levels in juveniles were found in studies on, for example helmeted guineafowl (Crowe 1977;Junker et al 2008b), herons (Sitko and Heneberg 2015) and arctic-breeding waterfowl (Amundson et al 2016), and may be a result of age-dependent morphological differences as well as a poorly developed juvenile immune system and consequently lower resistance to infection. Moore et al (1987) found host age to be an occasionally important factor with regard to helminth prevalence and density in northern bobwhites, whereas Shea et al (2021) found no effect of host age on helminth infection in the same host species. In yet other instances, for example in ruffed grouse (Kalla et al 1997), infection patterns of helminth species or communities were best explained by age and sex interaction.…”

“…Some studies recorded male bias in grouse (Isomursu et al 2006) and arctic-breeding waterfowl (Amundson et al 2016), whereas a few studies reported female bias, for example in helmeted guineafowl (Davies et al 2008) and birds of prey (Santoro et al 2012). Yet, other studies found no effect of host sex on infection patterns in northern bobwhites (Moore et al 1987;Villareal et al 2016;Bruno et al 2019;Shea et al 2021), helmeted guineafowl (Crowe 1977;Junker et al 2008b) or red-legged partridges (Calvete et al 2003). Host sex-dependent variation in helminth infections may be expected due to sexual size dimorphism and between sex behavioural and hormonal differences, especially the immunosuppressive influence of testosterone (Santoro et al 2012;Sitko and Heneberg 2015;Amundson et al 2016).…”

“…In recent years, gamebirds (Galliformes) have become the focus of several helminth community studies, because of the important role they play in the hunting industry in numerous countries worldwide (Calvete et al 2003;Isomursu et al 2008;Bruno et al 2019). Many of these studies investigated the influence of host sex and age on helminth community patterns in various avian species, as potentially two of the main drivers of variation in helminth infection (Kalla et al 1997;Calvete et al 2003Calvete et al , 2004Isomursu et al 2006Isomursu et al , 2008Landgrebe et al 2007;Amundson et al 2016;Nielsen et al 2020;Shea et al 2021). Age and sex differences are mitigated via two main routes, either exposure or susceptibility to parasites (Nielsen et al 2020).…”