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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
), hereaer
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 signicance of bobwhite, has led to
concerted eorts aimed at investigating the factors contributing to
dwindling bobwhite numbers. While habitat loss, changing
agricultural practices, and dynamic weather patterns are known to
aect 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 eort
between several universities was launched in order to investigate the
eects that contaminants, diseases and parasites have on quail. is
initiative, known as Operation Idiopathic Decline (OID), revealed
signicant 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 inammation 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 suered 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
eects 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 inuenced 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 aect 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 eect 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 eect 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 eects 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 dicult to observe and identify parasite
induced host mortality (PIHM) in the wild [28].
Considering the ability of
T. tenuis
to aect red grouse populations,
it is possible that caecal worms and eyeworms may aect bobwhite
populations in the Rolling Plains in a similar manner. However,
determining the signicance and extent to which this occurs may also
take considerable time and eort, 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 eects
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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Rolling Plains Ecoregion of West Texas. Arch Parasitol 2: 115.
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