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Potential parasite induced host mortality in Northern bobwhite (Colinus virginianus) from the Rolling Plains ecoregion of West TExas

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Anecdotal reports of Northern bobwhite quail (Colinus virginianus) exhibiting strange behavior have raised suspicions of parasite induced host mortality (PIHM) in the Rolling Plains of West Texas. In 2017, we received 11 bobwhite carcasses associated with such reports and found parasites in all of these specimens. While further research is needed to evaluate the impact of parasites on bobwhite, these reports provide a valuable supplement to on-going investigations of PIHM in bobwhite from the Rolling Plains of West Texas.
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Potential Parasite Induced Host Mortality in Northern Bobwhite (
Colinus
virginianus
) From the Rolling Plains Ecoregion of West Texas
Matthew Z Brym, Cassandra Henry and Ronald J Kendall*
The Wildlife Toxicology Laboratory, The Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas, USA
*Corresponding author: Ronald J Kendall, The Wildlife Toxicology Laboratory, The Institute of Environmental and Human Health, Texas Tech University, Box 43290,
Lubbock, Texas, 79409-3290, USA, Tel: 806-885-0238; Fax: 806-885-2132; E-mail: ron.kendall@ttu.edu
Received date: December 15, 2017; Accepted date: January 05, 2018; Published date: January 10, 2018
Copyright: ©2017 Brym MZ, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abstract
Anecdotal reports of Northern bobwhite quail (Colinus virginianus) exhibiting strange behavior have raised
suspicions of parasite induced host mortality (PIHM) in the Rolling Plains of West Texas. In 2017, we received 11
bobwhite carcasses associated with such reports and found parasites in all of these specimens. While further
research is needed to evaluate the impact of parasites on bobwhite, these reports provide a valuable supplement to
on-going investigations of PIHM in bobwhite from the Rolling Plains of West Texas.
Short Communication
e Northern bobwhite quail (
Colinus virginianus
), hereaer
bobwhite, is a popular game bird found throughout much of the
United States. Bobwhite are particularly well known in Texas, where
hunters dedicate substantial resources to the pursuit of these birds,
thereby providing valuable revenue for local communities [1].
Unfortunately, over the past several decades, bobwhite have been
declining throughout their range, including Texas [2]. is decline,
coupled with the economic signicance of bobwhite, has led to
concerted eorts aimed at investigating the factors contributing to
dwindling bobwhite numbers. While habitat loss, changing
agricultural practices, and dynamic weather patterns are known to
aect bobwhite abundance [3-5], continued declines in areas with
relatively stable conditions [6] suggest that other factors may also be at
play. Despite the urging from Robel [7], Brennan [8], and Peterson [9]
to investigate other factors such as disease and parasites, these factors
remained undervalued and were not considered a priority in the
investigation of the bobwhite decline.
However, when there was a rapid and mysterious decline in quail
abundance in the Rolling Plains of Texas and Oklahoma in 2010, an
area long considered to be a stronghold for quail, a collaborative eort
between several universities was launched in order to investigate the
eects that contaminants, diseases and parasites have on quail. is
initiative, known as Operation Idiopathic Decline (OID), revealed
signicant parasitic infection in bobwhite from the Rolling Plains
[10,11]. e most common parasites found in studies associated with
OID were the caecal worm (
Aulonocephalus pennula
) and eyeworm
(
Oxyspirura petrowi
), which are heteroxenous nematodes that infect
the caeca and eyes, respectively, of their hosts [12,13]. Both of these
helminths were found to be highly prevalent, with Bruno [10]
documenting infection rates of caecal worms and eyeworms in
bobwhite from the Rolling Plains of Texas as high as 91% and 66%
respectively. Additional studies have documented that in some areas
infection rates can be 100% for both parasites [14,15]. Such a high
incidence of these parasites caused concerns, which were later elevated
following evidence of pathological consequences of eyeworm infection
[16,17].
Figure 1: From the Rolling Plains ecoregion of Texas, 11 samples
were donated from (A) Kent (n=1), (B) Stonewall (n=9), and (C)
Fisher (n=1) counties.
e discovery of inammation and damage to the cornea and eye
tissues of infected bobwhite led to speculation of visual impairment,
and Dunham et al. [17] further suspected that eyeworm infection
could reduce the survivability of birds. Considering the high infection
rates observed in the Rolling Plains, this is a concerning hypothesis.
ese ndings also complement prior observations of peculiar
behavior in bobwhite from the region. For example, some quail were
seen running in circles when pursued by hunting dogs, leading
observers to believe that they may have suered impaired vision [18].
Additionally, anecdotal reports from ranchers and land owners in the
Rolling Plains detailed instances of bobwhite ying into barns and
other anthropogenic structures, with eyeworms found emerging from
the eyes of these quail upon inspection (Personal communication,
Kendall). While interesting, care must be taken when considering such
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Archives of Parasitology Brym et al., Arch Parasitol 2018, 2:1
Short Communication Open Access
Arch Parasitol, an open access journal Volume 2 • Issue 1 • 1000115
reports in terms of evaluating the impact of parasites, as they are not a
substitute for intensive study. However, such accounts can provide a
valuable supplement to systematic research, particularly in cases where
the specimen(s) associated with the account are available for
examination.
In this communication, we will discuss several reports of bobwhite
mortalities that were associated with specimens donated to the Wildlife
Toxicology Laboratory (WTL) at Texas Tech University. Since 2013,
the WTL has been engaged in research following the prevalence and
eects of parasites in bobwhite from the Rolling Plains of West Texas
[11]. Occasionally, bobwhites are donated to the WTL, and between 5
February and 25 November 2017, we received an unprecedented 11
carcasses from Fisher, Kent, and Stonewall counties in Texas (Figure 1).
Of these samples, 3 were observed ying into anthropogenic
structures, 3 collected as roadkill, 2 reportedly killed by Coopers
hawks (
Accipiter cooperii
), 2 hand captured, and 1 found with an
undetermined cause of death. e carcasses were necropsied and
examined for the presence of eyeworms and caecal worms as described
by Dunham et al. [14] under Texas Parks and Wildlife Research Permit
No. SPR-0715-095.
Bobwhite recovered post collision with anthropogenic structures
possessed bruising on the breast tissue suggesting that impact occurred
at a high speed. One sample recovered from Stonewall County was also
reported to have eyeworms emerging from underneath the nictitating
membrane at the time of collection. Eyeworms were found in all 3 of
these samples, and the report of eyeworms near the eye surface, in
conjunction with high impact speed, may be indicative of visual
disruption. Additionally, all of the road kill samples we received were
also infected with eyeworms, which may have contributed to collisions
as these were collected from private low speed and low volume roads.
ese observations parallel anecdotal reports and support Dunham et
al. [17] hypothesis of potentially disrupted vision resulting from
eyeworm infection. Consequently, additional studies are warranted to
determine whether eyeworms impair the vision of infected individuals
and if damage is relative to infection levels or is inuenced by the
position of eyeworms within the eye. Although such research would be
challenging to implement, it would provide crucial insight into the
dynamics of this parasite and its potential to compound with other
stressors that aect bobwhite survival, such as predators, scarcity of
food, and harsh climactic variables [6].
Figure 2: A) Breast from heavily parasitized bobwhite donated from Stonewall County, Texas showing severe emaciation. B) Breast of non-
infected bird.
Parasites may exacerbate the eect of these stimuli, particularly in
areas where infection is highly prevalent, such as the Rolling Plains.
e circumstances surrounding the following quail samples are
potential examples of how parasites may compound other variables.
For instance, 2 of our specimens that were reportedly killed by
Cooper’s hawks, a known predator of bobwhite [19], were infected
with eyeworms at what Dunham et al. [14] considered mild and strong
infections. Unfortunately, one of the caeca was not recovered, but the
other had a strong caecal worm infection. Furthermore, it was
speculated that the quail with an undetermined cause of death was also
a hawk kill as it was found with neck damage and blood pooled around
the head. is quail’s ability to escape predators may have been
impaired as well as it had an extreme eyeworm infection and strong
caecal worm infection. While it is unknown whether these parasites
contributed to these examples of predation, it is possible that parasites
impair the quail’s ability to evade such a competent predator.
e remaining 2 samples were given to the WTL by ranchers who
were able to approach and capture the quail by hand, a truly unusual
phenomenon. One of these birds, collected from Stonewall County on
25 June 2017, was severely emaciated (Figure 2A) and harbored a
strong eyeworm and extreme caecal worm infection. e caecal worm
numbers in the second bird were also high and approached an extreme
level. Rollins [20], Dunham et al. [21], and Henry et al. [22] postulated
that high caecal worm numbers could impede caecal function and lead
to malnutrition. Furthermore, Lehmann [23,24] noted that increased
caecal worm burdens were associated with decreased vitamin A levels.
As such, it is possible that parasites contributed to the condition of the
hand captured birds and continued research into the consequences of
these parasites is important in understanding their eect on bobwhite
survival.
e omnipresence of eyeworms and caecal worms in bobwhite
donated to the WTL in 2017, coincided with increased parasite
Citation: Brym MZ, Henry C, Kendall RJ (2018) Potential Parasite Induced Host Mortality in Northern Bobwhite (Colinus virginianus) From the
Rolling Plains Ecoregion of West Texas. Arch Parasitol 2: 115.
Page 2 of 3
Arch Parasitol, an open access journal Volume 2 • Issue 1 • 1000115
burdens that may have resulted in a die-o of bobwhite in Mitchell
County, Texas [15], and potentially the Rolling Plains. ese
observations, as well as the reports associated with donated specimens,
augment anecdotal accounts from throughout the Rolling Plains,
highlighting the potential of these parasites to impact bobwhite
abundance in the region. Although the eects of parasites on bobwhite
of the Rolling Plains are still under investigation, another helminth,
(
Trichostrongylus tenuis
), has been found to drive the population
cycles of the red grouse (
Lagopus lagopus scotica
) by reducing
fecundity and increasing vulnerability to predators [25-27]. ese
ndings for the red grouse required over 20 years of extensive research
because it is notoriously dicult to observe and identify parasite
induced host mortality (PIHM) in the wild [28].
Considering the ability of
T. tenuis
to aect red grouse populations,
it is possible that caecal worms and eyeworms may aect bobwhite
populations in the Rolling Plains in a similar manner. However,
determining the signicance and extent to which this occurs may also
take considerable time and eort, particularly since the impact of
multiple parasites is not well understood. Furthermore, instances of
hosts exhibiting terminal symptoms of parasitic infection are rarely
observed in the wild [28], and bobwhite carcasses, which may hold
evidence of PIHM, are seldom found even in areas where quail are
common [29] and are typically scavenged within 24 h [30]. For this
reason, continued donations of specimens are essential to the
investigation of PIHM of bobwhite in the Rolling Plains. While the
ndings presented in this communication represent a small sample
and are not a substitute for systematic research, they do provide a
valuable complement to research investigating PIHM in bobwhite from
the Rolling Plains. erefore, a comprehensive approach involving
systematic lab and eld work, in conjunction with personal accounts
and observations, may yield an improved understanding of the eects
multiple parasites have on bobwhite populations.
Acknowledgements
We thank Park Cities Quail and the Rolling Plains Quail Research
Foundation for the funding and support necessary to conduct this
research. We also thank those that donate bobwhite to the WTL.
Without their constant vigilance and dedication, this research would
not be possible.
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Citation: Brym MZ, Henry C, Kendall RJ (2018) Potential Parasite Induced Host Mortality in Northern Bobwhite (Colinus virginianus) From the
Rolling Plains Ecoregion of West Texas. Arch Parasitol 2: 115.
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Arch Parasitol, an open access journal Volume 2 • Issue 1 • 1000115
... Numerous surveys of parasites infecting bobwhite throughout their range exist, but more recently, several studies have focused on the possible impacts of Aulonocephalus pennula (caecal worm) and Oxyspirura petrowi (eye worm) on bobwhite health (Bruno et al., 2019;Brym et al., 2018aBrym et al., , 2018bDunham et al., 2016aDunham et al., , 2016bDunham et al., 2017aDunham et al., , 2017bShea et al., 2020;Villarreal et al., 2016). These authors speculated that high intensity infections with A. pennula and O. petrowi increases morbidity and mortality of infected bobwhite, although these studies are geographically limited as most were conducted in Texas Dunham et al., 2016aDunham et al., , 2016bDunham et al., 2017aDunham et al., , 2017bHenry et al., 2017;Brym et al., 2018b;Kalyanasundaram et al., 2019). ...
... study in Texas reported a much higher average intensity of 599 worms (Brym et al., 2018a). These mean intensities reported in bobwhite in Texas are much higher than what we observed in our study. ...
... However, we observed that a negative relationship among bobwhite fat and A. pennula intensity. In those areas of Texas where the average worm intensity is well over 300 worms and nearly every bobwhite sampled is infected (Brym et al., 2018a;Henry et al., 2017), this parasite could be a health concern. Bobwhites with lower fat stores are less likely to survive through periods of adverse environmental conditions including reduced food availability as well as potential nutritional deficiencies due to severe A. pennula infections; the latter has been described in bobwhite inhabiting the Rolling Plains ecoregion of Texas (Brym et al., 2018b). ...
... This decline has received increasing attention in the Rolling Plains Ecoregion of West Texas, considered one of the last strongholds of this popular gamebird [2]. In this region, parasites have been an especially notable concern due to the prevalence of two heteroxenous nematodes, the eyeworm (Oxyspirura petrowi Skrjabin, 1929) and caecal worm (Aulonocephalus pennula Chandler, 1935), infecting bobwhite [3][4][5][6]. ...
... Common methods of assessing parasite prevalence in bobwhite have largely consisted of necropsies (e.g. [3,4,6,7]) which can involve time, money, and intense labor. Similar problems arise when using fecal floats as a nonlethal alternative, with the additional risk of potentially misidentifying parasite species' eggs [8]. ...
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Over the last few decades, there has been a decline in Northern bobwhite quail (Colinus virginianus) throughout their native range. While there are various factors that may be influencing this decline, it is suggested that parasites should be taken into consideration as a potential contributor in the Rolling Plains Ecoregion. High prevalence of the eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) in bobwhite of this region, coupled with a continuous decline, creates a need to assess infection through alternative methods for regional surveillance. Previous studies have developed a qPCR method and mobile research laboratory as an option for nonlethal procedures. However, there is still a need for standardization of these techniques. Therefore, this study builds on previous protocols to develop an application that considers factors that may influence qPCR results. In this study, cloacal swabs are collected from bobwhite in three locations throughout the Rolling Plains and scaled based on amount of feces present on the swab. This data is compared to qPCR standards as a limit of quantification for both eyeworm and caecal worm to define parasitic infection levels. Binary logistic regressions confirm that the probability of detection increases for both eyeworm (Odds Ratio: 2.3738; 95% Confidence Interval: [1.7804, 3.1649]) and caecal worm (Odds Ratio: 2.8516; 95% Confidence Interval: [2.2235, 3.6570]) as swab score increases. Infection levels for eyeworm and caecal worm are based on the generated cycle threshold value averages of qPCR standards. Based on the results of this study, this method can be applied in the mobile research laboratory to quantitatively assess regional parasitic infection in bobwhite throughout the Rolling Plains.
... It has been proposed that heavy infection by caecal worms could lead to malnutrition in bobwhite (Dunham et al., 2017b), which may hinder survival, whereas eyeworms, which are found in the tissues around the eye, can cause cellular damage to the eye tissues, as well as scarring and interstitial keratitis of the cornea (Bruno et al., 2015;Dunham et al., 2016). Bobwhite infected with eyeworms have therefore been hypothesized to have impaired vision, which is supported by anecdotal reports of abnormal behavior like bobwhite flying into large structures (Brym et al., 2018a). ...
... For example, Henry et al. (2017) found evidence of a die-off among bobwhite that corresponded to higher infection levels of caecal and eyeworms than seen in previous years. Furthermore, drought is suggested to exacerbate caecal worm intensity in bobwhite (Lehmann, 1984), and high caecal worm intensities have been reported in bobwhite during periods of drought (Brym et al., 2018a;Brym et al., 2018b). These high intensities may have negative impacts on bobwhite populations considering drought has increased in the past decade and will continue to increase in the Rolling Plains (Modala et al., 2017). ...
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The Northern bobwhite quail (Colinus virginianus) is an important gamebird among hunters that has been experiencing a nationwide decline for N 50 yr. In West Texas, one of the last regions to experience this downward trend, research on bobwhite populations has focused on habitat variables and, increasingly, on parasitic infection. In bobwhite, two of the most common parasites are the caecal worm (Aulonocephalus pennula) and eyeworm (Oxyspirura petrowi). To better document the state of bobwhite populations in the Rolling Plains Ecoregion, trapping , summer rooster counts, fall covey counts, and parasitic infection assessments were conducted in three counties during 2018. These efforts were compared with previous years for a longitudinal perspective. In 2018, bobwhite populations experienced a widespread decline, although some counties surveyed fared slightly better than others. More effort was required to trap fewer total bobwhite, and fewer roosters and coveys were counted than in previous years. In addition, in 2018, parasitic infection levels of caecal and eyeworms were higher than or similar to levels in previous years. Additional research is necessary to understand which factors influence bob-white populations in allopatric locations and over time.
... Farming not only changes the habitat and increases fragmentation, possibly making it less favorable for foraging or nesting success or predator avoidance, but also may cause potential exposures to toxicants (e.g., pesticides), which can result in negative effects (Palmer and Bromley 1992;Richardson et al. 2020). In addition, many historical studies on parasites and pathogens have shown that pathogens may be a health threat (King et al. 1981; Wilson and Crawford 1988;Turaga et al. 2016;Dunham et al. 2017;Brym et al. 2018;Bruno et al. 2019;Shea et al. 2021). However, contemporary studies on free-ranging bobwhite quail have primarily focused on parasites or specific infectious agents (e.g., influenza virus, West Nile virus [WNV], intestinal microbiota) or were limited in geographic scope (Ferro et al. 2012;Urban et al. 2013;Su et al. 2014). ...
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The Northern Bobwhite (Colinus virginianus) has been undergoing a range-wide population decline. Potential causes for declines across its historic range have been investigated for decades and include habitat loss and fragmentation and a variety of parasitic and infectious diseases. Although there have been studies on bobwhite ecology in Oklahoma, USA, relatively little is known about parasites and pathogens in the region. We evaluated the health of free-ranging bobwhites from nine sites in western Oklahoma. From 2018 to 2020, 206 bobwhites were evaluated for gross and microscopic lesions and tested for selected pathogens. In general, bobwhites were in good nutritional condition with ample muscle mass and fat stores. No significant gross lesions were observed in any bobwhite and no significant histologic lesions were detected in a subset. There was no evidence of infection with or exposure to reticuloendotheliosis virus, West Nile virus, respiratory Mycoplasmataceae species, Pasteurella multocida, intestinal Eimeria spp., or oral Trichomonas spp. Several pathogens of potential concern were detected, including avian adenovirus (8.6%), Toxoplasma gondii (2.3%), and haemosporidians (a Haemoproteus sp. (1.5%), Leucocytozoon schoutedeni (1.5%), and Plasmodium homopolare haplotype 2 [lineage LAIRI01; 3.6%]). Physaloptera sp. (12%) and Sarcocystis sp. (1%) were detected in the breast muscle. Low intraspecific genetic diversity was noted for Physaloptera sp., and sequences were most similar to Physaloptera sequences from bobwhites and grasshoppers (Orthoptera) in Texas. Low intensities of chewing lice, chiggers, and ticks were observed. A subset of bobwhites had evidence of exposure to selected toxicants and heavy metals; a small number had low levels of iron, manganese, zinc, molybdenum, and copper, which were not considered diagnostically relevant. In general, bobwhites from western Oklahoma appeared to be in good health with a low diversity of pathogens detected, but future work is needed to understand potentially changing disease risks for this population.
... Moreover, phylogenetic analyses have revealed the close relation of O. petrowi to the human eyeworm (Loa loa) [16,17] and the human and carnivore eyeworm (Thelazia callipaeda) [17], which have been associated with impaired vision [18] and ulcerative keratitis [19] in their hosts, respectively. While the phylogenetic similarity of O. petrowi to L. loa and T. callipaeda does not necessarily imply similar pathology, the documented pathological consequences of O. petrowi infection alongside reports of bobwhite flying into stationary objects [20,21] suggest that impaired vision may occur in birds infected with this parasite. [19,22,23], while the chicken eyeworm (Oxyspirura mansoni) utilizes the Surinam cockroach (Pycnoscelus surinamensis) for this purpose [24]. ...
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Background: Oxyspirura petrowi (Spirurida: Thelaziidae), a heteroxenous nematode of birds across the USA, may play a role in the decline of the northern bobwhite (Colinus virginianus) in the Rolling Plains Ecoregion of West Texas. Previous molecular studies suggest that crickets, grasshoppers and cockroaches serve as potential intermediate hosts of O. petrowi, although a complete study on the life-cycle of this nematode has not been conducted thus far. Conse-quently, this study aims to improve our understanding of the O. petrowi life-cycle by experimentally infecting house crickets (Acheta domesticus) with O. petrowi eggs, feeding infected crickets to bobwhite and assessing the life-cycle of this nematode in both the definitive and intermediate hosts.Methods: Oxyspirura petrowi eggs were collected from gravid worms recovered from wild bobwhite and fed to house crickets. The development of O. petrowi within crickets was monitored by dissection of crickets at specified intervals. When infective larvae were found inside crickets, parasite-free pen-raised bobwhite were fed four infected crickets each. The maturation of O. petrowi in bobwhite was monitored through fecal floats and bobwhite necropsies at specified intervals.Results: In this study, we were able to infect both crickets (n = 45) and bobwhite (n = 25) with O. petrowi at a rate of 96%. We successfully replicated and monitored the complete O. petrowi life-cycle in vivo, recovering embryonated O. petrowi eggs from the feces of bobwhite 51 days after consumption of infected crickets. All life-cycle stages of O. petrowi were confirmed in both the house cricket and the bobwhite using morphological and molecular techniques.Conclusions: This study provides a better understanding of the infection mechanism and life-cycle of O. petrowi by tracking the developmental progress within both the intermediate and definitive host. To our knowledge, this study is the first to fully monitor the complete life-cycle of O. petrowi and may allow for better estimates into the potential for future epizootics of O. petrowi in bobwhite. Finally, this study provides a model for experimental infection that may be used in research examining the effects of O. petrowi infection in bobwhite. (PDF) Life-cycle of Oxyspirura petrowi (Spirurida: Thelaziidae), an eyeworm of the northern bobwhite quail (Colinus virginianus). Available from: https://www.researchgate.net/publication/337430813_Life-cycle_of_Oxyspirura_petrowi_Spirurida_Thelaziidae_an_eyeworm_of_the_northern_bobwhite_quail_Colinus_virginianus [accessed Nov 22 2019].
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Parasites are ubiquitous in wildlife populations and can cause reduced fecundity and survival in several species, as well as influence cyclic population fluctuations. Anthelmintic treatment has been found to mitigate these negative effects of parasites in many wild populations. It is suspected that the eyeworm Oxyspirura petrowi and caecal worm Aulonocephalus pennula are negatively affecting northern bobwhite quail (Colinus virginianus) populations in semiarid ecoregions of Texas. However, it is difficult to determine the effect of parasites on a population without experimentally reducing the parasite. The purpose of this study was to test the efficacy of an anthelmintic medicated feed at reducing parasite burden in wild bobwhite as part of a series of studies for United States Food and Drug Administration (USFDA) registration. Two pilot studies found that the medicated feed had a 71.5% and 81.7% efficacy against caecal worms and eyeworms, respectively, and significantly reduce total parasite burdens (p < .05). For the final efficacy study, control or medicated feed was randomly assigned to 12 feeding systems on a private ranch and administered for 21 consecutive days to determine the efficacy of anthelmintic treatment of eyeworms and caecal worms in bobwhite. Up to five bobwhite were collected and assessed for parasite abundance from each feeding system following the 21-day treatment to assess efficacy. There was a significant difference for caecal worms between treated and control bobwhite (p < .0001), with a 99.5% efficacy. This demonstrates that the medicated feed is a viable method for reducing parasites in wild bobwhite and could be used to elucidate the impacts of parasites on bobwhite populations.
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Helminths, in particular eyeworms (Oxyspirura petrowi) and cecal worms (Aulonocephalus pennula), may be a factor influencing northern bobwhite (Colinus virginianus) populations in Texas. Previous research has shown a discrepancy in helminth infections between the Rolling Plains and Rio Grande Plains of Texas, US, potentially caused by differences in intermediate host distribution and abundance. We explored an alternative hypothesis centered on plant diversity, given that many plants possess phytochemicals with anthelmintic properties. We predicted that plant diversity would be greater and bobwhite diet more diverse in the Rio Grande Plains than the Rolling Plains, which in turn would potentially expose bobwhites to more plants with anthelmintic properties and therefore result in lower parasite prevalence and intensity. We conducted a literature review of plant diversity, anthelmintic plants, and bobwhite diet in Texas to explore this hypothesis. We also quantified the relationship between helminth prevalence in bobwhites and latitude. We documented trends for higher plant species richness, greater number of anthelmintic plants, and more diverse bobwhite diet in the Rio Grande Plains compared to the Rolling Plains. In addition, we documented a trend for increasing helminth prevalence with latitude for eyeworms but not cecal worms. Our study provides circumstantial evidence supporting the plant-diversity hypothesis and warrants experimental testing.
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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.
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The potential of parasites to affect host abundance has been a topic of heated contention within the scientific community for some time, with many maintaining that issues such as habitat loss are more important in regulating wildlife populations than diseases. This is in part due to the difficulty in detecting and quantifying the consequences of disease, such as parasitic infection, within wild systems. An example of this is found in the Northern bobwhite quail (Colinus virginanus), an iconic game bird that is one of the most extensively studied vertebrates on the planet. Yet, despite countless volumes dedicated to the study and management of this bird, bobwhite continue to disappear from fields, forest margins, and grasslands across the United States in what some have referred to as “our greatest wildlife tragedy”. Here, we will discuss the history of disease and wildlife conservation, some of the challenges wildlife disease studies face in the ever-changing world, and how a “weight of evidence” approach has been invaluable to evaluating the impact of parasites on bobwhite in the Rolling Plains of Texas. Through this, we highlight the potential of using “weight of the evidence” to better understand the complex effects of diseases on wildlife and urge a greater consideration of the importance of disease in wildlife conservation.
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We have been monitoring wild Northern bobwhite quail (Colinus virginianus) on a research transect in Mitchell County, Texas. We captured a total of 51 bobwhites in March-May of 2016 and 2017 and examined them for eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) infections. In March 2017, bobwhites averaged 15 ± 10 eyeworms and 269 ± 90 caecal worms, and by mid-April averages had increased to 18 ± 13 eyeworms and 372 ± 144 caecal worms. These averages were much higher than those observed in March 2016 (11 ± 13 eyeworms and 160 ± 57 caecal worms) and April 2016 (12 ± 12 and 216 ± 56, respectively). We observed a precipitous decline in quail numbers by late April 2017, and average infection had dropped to 7 ± 2 eyeworms and 252 ± 109 caecal worms. The number of trapping sessions needed to capture one bobwhite also increased from 14.26 in 2016 to 36.46 in 2017. These observations warrant further investigation into the effects these helminth parasites may have on bobwhites and their populations within the Rolling Plains.
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Parasitic nematodes that infect quail have been understudied and long been dismissed as a problem in quail management. Within the Rolling Plains ecoregion of Texas, an area that has experienced quail population “boom and bust” cycles and ultimately a general decline, the need to determine why Northern bobwhite (Colinus virginianus) populations are diminishing has increased in priority. Previously, caecal parasites have been documented to cause inactivity, weight loss, reduced growth, inflammation to the caecal mucosa, and even death. The caecal worm Aulonocephalus pennula is an intestinal nematode parasite that is commonly found within the caecum of quail, as well as many other avian species. In the Rolling Plains ecoregion, A. pennula has been documented to have as high as a 98% prevalence in bobwhite quail samples; however, the effect it has on its host is not well understood. The present study documents A. pennula causes no pathological changes within the caeca of the Northern bobwhite. However, there is concern for disruption of digestion and the possible implications of infection for wild bobwhite quail survival are discussed.
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Debilitating ocular diseases are often reported in avian species. By and large, helminth parasites have been overlooked in avian diseases and regarded as inconsequential. The decline of Northern bobwhite quail (Colinus virginianus) in the Rolling Plains ecoregion of Texas has prompted an investigation of the factors influencing their disappearance. Infection by the eyeworm (Oxyspirura petrowi) has been documented in many avian species; however, the effect it has on its host is not well understood. Heavy eyeworm infection has been documented in Northern bobwhites throughout this ecoregion, leading to eye pathology in this host species. The present study further documents and supports the pathological changes associated with O. petrowi in bobwhites.
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Northern bobwhite (Colinus virginianus) and scaled quail (Callipepla squamata) have experienced chronic declines within the Rolling Plains ecoregion of Texas. Parasitic infection, which has long been dismissed as a problem in quail, has not been studied thoroughly until recently. A total of 219 northern bobwhite and 101 scaled quail from Mitchell County, Texas were captured and donated from 2014-2015, and examined for eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) infections. In 2014, bobwhites averaged 19.6±1.8 eyeworms and 98.6±8.2 caecal worms and 23.5±2.1 eyeworms and 129.9±10.7 caecal worms in 2015. Scaled quail averaged 4.8±1.0 eyeworms and 50±6.8 caecal worms in 2014 and 5.7±1.3 eyeworms and 38.1±7.1 caecal worms in 2015. This study expands the knowledge of parasitic infection in quail inhabiting the Rolling Plains of Texas. A significant difference was documented in O. petrowi infection between species but there was no significant difference in A. pennula between quail species. No significant difference was detected in parasite infection between the sexes of both northern bobwhite and scaled quail. This study also documented the highest reported O. petrowi infection in both species of quail. Additional research is needed on the life history and infection dynamics of O. petrowi and A. pennula infections to determine if there are individual and/or population level implications due to parasitic infection. .
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The Rolling Plains have historically provided some of the best opportunities to hunt northern bobwhite (Colinus virginianus) populations anywhere. Historically, scaled quail (Callipepla squamata) have been common to abundant over much of the Rolling Plains, but the populations decreased dramatically in the late 1980s and have been slow to reclaim their historic range. Copyright © 2007 by Leonard Alfred Brennan Manufactured in the United States of America All rights reserved.