Written by Krista Ruppert, Texas A&M WFSC ‘16
Edited by Amanda Gobeli, Texas A&M AgriLife Extension Associate
A
parasitic relationship is one in which one organism benefits at the cost of
another. Given that quail are susceptible to parasitism, an
understanding of the effects of parasites on quail health may be essential in attempts to reverse the quail decline. A push to study quail parasites began in the mid-1980s and has
slowly made its way into Texas; despite this, few recent studies have been done on the impacts of parasites on quail and many are outdated. While there is still plenty to learn, the data
already collected is invaluable as it fills a void in knowledge of quail
ecology.
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An eyeworm is
visible on this dead male northern bobwhite collected in Roberts County.
Photo from Texas A&M AgriLife Extension
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Quail parasites can be categorized into several groups: external parasites such as lice and ticks, intestinal parasites such as cestodes and enteric nematodes, eyeworms, and disease-causing agents such as protozoans, bacteria, and viruses. External
parasites are ubiquitous among all species of quail. Almost every individual will
be afflicted with fleas, mites, ticks, or lice to some degree. Chewing lice in particular are common among quail,
with several species having high infestation rates. Gonoides ortygis is estimated to occur
on 45-78% of bobwhites, while G. squamatus
is estimated to occur on 78% of scaled quail. Oxylipeurus clavatus has been estimated to affect 38-82% of
bobwhites, while O. callipeplus has
been estimated to affect 63-95% of scaled quail. Finally, Colinicola pallida has been observed to affect 55-100% of scaled
quail. Taking into account the overlap of species on individuals, it would be difficult to find a quail entirely lacking chewing lice!
Ticks are also variably
prevalent on quail; however they are less common in areas populated by red
imported fire ants. Ticks from the genus Amblyomma and Haemaphysalis
have both been documented occurring on bobwhites, with occurrence estimated at
2-100% for A. americanum, 4-77% for A. maculatum, 44-100% for H. chordeilis, and 8-94% for H. leporispalustris, which has also been
estimated to occur on 85% of scaled quail. In addition to the red imported fire ants mentioned above, prevalence
of parasites is also dependent on season, weather, and area, making a firm
estimate for the entire state of Texas difficult to achieve. Data is lacking
for Gambel’s quail, Montezuma quail, and, to a degree, scaled quail; however, it
is extremely likely that they also carry various species of chewing lice and
ticks.
Though chewing lice and ticks are prevalent on Texas quail, research
has not yet been completed on the effects of these parasites on the health of
the birds. There are theories on both sides of the debate, with some
hypothesizing that these parasites are detrimental to quail and others
postulating that they have no major influence on health.
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The tick A. americanum is a common external
parasite of northern bobwhite.
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Internal
parasites are also common in quail, and cestodes, more commonly known as
tapeworms, are no exception. The varieties most often found in bobwhites are members of the
genus Raillietina. R. cesticillus has
been reported in 15-44% of bobwhites, with a greater
infection rate for quail found in high densities. R. tetragona and R. colina
have also been documented in bobwhites at rates ranging from 38-73%. Cestodes
have been previously found to infect scaled quail, but have not yet been
documented in Gambel’s or Montezuma quail in Texas. Severe tapeworm infestations may cause intestinal obstruction and death in quail; however, small numbers have not yet been
found to be harmful to a bird's health.
Enteric nematodes are also
frequently present in the digestive tracts of quail. Aulonocephalus lindquisti, a roundworm, is estimated to affect 80%
of bobwhites (particularly in the Gulf Prairies and Marshes) and up to 100% of
scaled quail, with an average of 15-40 parasites per bird but with documented
highs at over 300. This parasite has also been found in Gambel’s quail, most
commonly in the cecal pouches. A. pennula
has been documented at rates of 78% of bobwhites and 98% of scaled quail. This
parasite is more commonly found in quail that use spreader
dams, and intense infections may cause distention of the ceca and proventriculitis,
or inflammation of the glandular region between the crop and the gizzard. Other
common enteric nematodes include Tetrameres
pattersoni in 10-27% of bobwhites, the presence of which causes proventriculitis
regardless of numbers, and Trichostrongylus
spp. in 81-95% of bobwhites, which is not particularly pathogenic.
Of
particular note when discussing parasites of quail is the eyeworm,
Oxyspirura petrowi. This is a species
of nematode most frequently found in the nictitating membrane of a quail's eyes, and it has been recorded as occurring in a range of 9-100% of bobwhites,
2-56% of scaled quail, and 60% of Montezuma quail in Texas at rates of up to 40 worms
per bird. It has not yet been documented in Gambel’s quail. Parasite densities vary based on season and location, with the highest numbers
occurring in August and, once again, in birds using
spreader dams. While the effects of these parasites on quail are still being
studied, they may increase mortality indirectly by obscuring a bird's vision.
Additionally, the presence of more than ten worms will often lead to packed
parasites in lacrimal ducts, which causes swelling, inflammation, petechial
hemorrhaging (broken capillaries), and increased fibrosis (scarring of the
connective tissue). Quail may be affected even if there is no outward sign of
infection, and the presence of even a single worm will lead to some degree of
inflammation and potential tissue damage. See the blog post Quail
Parasites for more
information concerning eyeworms.
Though
protozoans, bacteria, and viruses may seem to be a far cry from the easily
visible worms, lice, and ticks previously discussed, these microparasites also have notable effects on quail, particularly in a captive, pen-reared
environment. The protozoan Trichomona
gallinae may cause trichomonosis in bobwhites, which has a mortality rate of
75% in 11 days, but is not particularly common in quail. Doves are hosts for
the disease, which spreads through mouth-to-mouth contact or infected feed and
water. Bobwhites have relatively low rates of infection despite sharing feed and water with infected doves, leading some to believe they are naturally resistant (though not immune) to the pathogens. Another protozoan, Histmonas
meleagridis, is transmitted by the cecal threadworm H. gallinarium and causes the disease
histomoniasis. In pen-reared bobwhite, an outbreak can lead to 75% of birds
being affected and 50% mortality, but it is less common in wild bobwhite.
Bacterial, viral and fungal infections also pose a threat to quail. Pasteurella multocida causes the disease avian cholera, which has a 99% mortality rate in captive bobwhites within 6 days. A vaccine has been developed to protect chickens from this particular illness, but the treatment is lethal to bobwhites, making exposure to the bacteria
especially dangerous for quail. It is not often found in wild quail as they usually live in much lower densities, making it difficult for the bacteria
to spread. Clostridium colinum is the
bacteria that cause ulcerative enteritis, which is widely considered to be the
most important disease of captive bobwhites, but it has not yet been documented
in free-living quail. Avian poxvirus is a virus documented as affecting
bobwhite and scaled quail and that is identifiable by the presence of lesions. Lesion on the
legs and wings cause few problems for the bird, but facial lesions interfere with feeding and can potentially lead to death. Most frequently, lesions are
found on the wings and are especially common during spring and summer,
coinciding with prevalence of mosquitos—an important mechanical
vector for the virus. The significance of avian poxvirus on quail populations
is as of yet unknown. Quail may also be affected by fungal aflatoxins from supplemental feed. Overall, microparasites are a greater concern for captive
birds than they are for free-living quail.
Disease
and parasites are an important but understudied area of quail research,
particularly given the lack of knowledge on their ecological significance and effects on individual birds. Further investigation is vital to understanding the relationships between parasites,
hosts, and populations. A
number of factors likely contribute to the ongoing quail decline in Texas, and although parasites are a fact of life for wild animals, their potential impacts should not be ignored. The presence and prevalence of parasites may provide valuable insights to guide quail conservation and management decisions.
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