Raising Pheasants - Avian Protozoal Diseases
Avian Protozoal Diseases
- Coccidiosis:
- Coccidiosis affects most species of poultry, waterfowl, gamebirds, and pigeons. The
information presented here will focus on the small chicken flock but the principles
discussed are generally applicable to other species. The typical history of a flock with
coccidiosis is that of increased mortality in a flock of young chickens (2 to 18 weeks of
age). Affected birds will be depressed, have ruffled feathers, be reluctant to move, and
often the feathers around the vent will be soiled with fecal material due to diarrhea. In
severe cases bloody droppings may be observed.
- Lesions
- A postmortem examination of a bird that has succumbed to coccidiosis will reveal
distinct pathology in one or more regions of the intestines. Coccidial species are both
highly host specific and infect a specific region of the intestines. Nine species of
coccidia infect chickens, three of these are most commonly associated with severe disease.
Eimeria acervulina affects the
duodenum and upper intestines, numerous small (0.5 to 1.0 mm) white foci can be seen on
the mucosal surface of the intestines and the intestinal wall is thickened. E. necatrix affects primarily the
middle portion of the small intestines; lesions include distinct white spots in the mucosa
(schizonts), ballooning of the intestines, and mucoid blood tinged intestinal contents. E. tenella infects the ceca of the
chicken and severe hemorrhage is seen in the cecal lumen with caseous cecal cores
developing in more chronic cases. Birds that recover from coccidiosis develop short lived
species specific immunity. With constant exposure to coccidial oocysts in the environment,
previously infected chickens do not develop clinical disease. Different avian species have
different, host specific, Eimeria spp.
Or Isospora spp. Renal coccidiosis
is seen in domesticated geese Eimeria
truncata as well as in some wild avian species.
- Diagnosis
- A diagnosis of coccidiosis can be established by preparing a wet mount of a mucosal
scraping from the intestines of an infected bird and examining it by light microscopy. The
coccidial oocysts and schizonts can readily be identified at 100X magnification. A fecal flotation is also very effective in demonstrating
coccidial oocysts. The specific species of coccidia involved in a disease outbreak can be
established by tissue tropism and oocyst morphology but this is not necessary as all
species respond well to the commonly used therapeutic agents.
- Treatment
- Coccidiosis is effectively treated with amprolium
in both chickens and turkeys. Amprolium is available in a 9.6% solution which is
administered in the drinking water at 0.024% for 3 to 5 days (1/3 oz. Of 9.6% amprolium
per gallon of drinking water). Once the flock has responded to treatment with amprolium
the dosage is lowered to 0.006% amprolium in the drinking water for an additional 1 to 2
weeks. An equally effective medication for the treatment of coccidiosis is sulfadimethoxine as per label instructions. Other
sulfa drugs are also effective in the treatment of coccidiosis but care must be taken with
all sulfa drugs to avoid toxicity and observe withdrawal times prior to slaughter.
- Prevention
- Once a farm has experienced an outbreak of coccidiosis it is extremely difficult to
eliminate the highly resistant coccidial oocysts from the environment. All subsequent
flocks must be kept on a coccidiosis prevention program. With layers and game birds,
raising the birds on wire can prevent coccidiosis. If well managed this practice will
break the coccidial life cycle. However, if birds are still able to reach their droppings
when raised on wire coccidiosis may still occur. Broilers raised on the ground or litter
are commonly fed coccidiostats (monensin, salinomycin, lasalocid, halofuginone,
nicarbazin, and amprolium) in the feed until slaughter. Care must be taken to observe the
appropriate feed withdrawal times. Layer pullets are often kept on a coccidiostat for the
first 16 weeks of life and then treated for disease if necessary later in life. Turkeys
are usually only kept on coccidiostats until 10 weeks of age as they are generally more
resistant to coccidiosis.
- Histomoniasis
- Definition
- Histomoniasis is a parasitic disease of gallinaceous birds characterized by sulfur
colored diarrhea, depression, anorexia and death. Histomoniasis is also called blackhead
in turkeys due to the cyanosis of the skin of the head, which occurs during the terminal
stages of this disease.
- Occurrence
- Histomoniasis has been reported in the USA, Canada, and Mexico, wherever susceptible
birds are present. Numerous gallinaceous birds are affected by histomoniasis with turkey,
chukar partridge, and ruffed grouse being severely affected. Species which will become
infected but may or may not develop severe disease include, chicken, peafowl, guinea fowl,
bobwhite quail, and pheasant.
- Etiology
- The etiologic agent of histomoniasis is Histomonas meleagridis a
protozoan which is sensitive to environmental conditions and all disinfectants. H.
meleagridis exists in two phases: nonamoeboidal and ameboidal. The amoeboidal phase
(8016 microns) is pleomorphic with numerous pseudopodia and is the "invasive"
phase during an infection. The "vegetative" phase (12-21 microns) is found in
the degenerating center of hepatic lesions and in the lumen of the intestines.
- The life cycle of H. meleagridis is intimately associated with the cecal nematode
of chickens, Heterakis gallinarum
and several species of earthworms found in the soil. The histomonads are able to persist
in the environment inside the heterakis egg to be ingested later by a susceptible host.
Likewise certain earthworms will ingest histomonad infected heterakis eggs and if eaten by
a susceptible avian host will serve as a transport host.
- Transmission and clinical signs
- The transmission of histomoniasis occurs primarily via heterakis eggs and earthworms as
described above but direct transmission by the ingestion of fresh droppings containing
viable histomonads may also occur.
- The chicken, often serving as an inapparent host to both heterakis and histomonads, is
considered the most important vector for histomoniasis. In commercial poultry operations
where poultry species are not mixed this no longer presents a problem but in multi-species
backyard flocks histomoniasis commonly occurs.
- The clinical signs of histomoniasis in turkeys include, sulfur-colored diarrhea,
depression, anorexia, cyanosis, and death. Mortality in affected young turkeys in high
(70-100%). In chickens sulfur-colored droppings are seldom seen but bloody droppings may
be observed. Mortality in chickens varies most commonly from 0-30%.
- Pathology
- The lesions of histomoniasis develop on the liver and ceca. During the initial phase of
infection a thickened hyperemic cecal wall with a serous/hemorrhagic exudate is found.
Caseation of this cecal exudate then occurs and a cheesy cecal core is formed. Ulceration
of the cecal wall often occurs in affected birds and this sometimes develops into a
perforated ceca and a generalized peritonitis. The hepatic lesions of histomoniasis are
large areas of hepatic necrosis (0.5-1.0 cm). These areas of hepatic necrosis have a
depressed center surrounded by a raised ring. "Bulls eye" hepatic lesions in
conjunction with caseous cecal cores are pathognomonic for histomoniasis.
- Histologically, a progressively more severe mixed inflammatory response is seen in an
infected ceca. Numerous bacteria, juvenile heterakis, and histomonads are commonly seen.
The cecal core is composed of sloughed epithelium, fibrin, erythrocytes, and leukocytes.
Coagulative necrosis and histomonad invasion may extend well into the muscular tunic of
the cecum. Large areas of hepatic necrosis/hepatitis are observed with many histomonads
observed in the peripheral area of the lesion.
- Diagnosis
- Histomoniasis can be diagnosed based on characteristic gross lesions and/or histologic
lesions.
- H. gallinarum can be isolated from tissues of freshly killed affected birds in
special broth media.
- Control
- The exclusion of chickens from turkey farms has drastically decreased the incidence of
this disease. In general turkey farms should be located on sites with dry, sandy, loose
soil. This type of soil contains fewer earthworms.
- Susceptible birds may be fed a histomoniasis preventative in the feed. Currently the
only available preventative is Histostat an arsenical which may cause slight growth
depression. The very effective blackhead preventatives/treatments emtryl (dimetridazol)
and Ipropan (ipronidazole) are no longer available in the United States. Metronidazole (Flagyl) can be used effectively in
the treatment of pet birds not intended for human consumption (peacocks or the pet
backyard turkey). An oral dose of 60 mg/kg body weight for 5 consecutive days is
effective. Treated birds should be moved to noncontaminated premises to prevent
reinfection.
- Trichomoniasis
- Definition
- Trichomoniasis is a disease of the upper digestive tract, seen in pigeons, doves,
raptors, turkeys, chickens as well as many other wild birds.
- Occurrence
- Trichomoniasis (Trich. For short) occurs frequently in pigeons and doves, as well as
raptors which feed upon them. The disease is called canker in pigeons and frounce in
falcons. With the current improved management practices in the poultry industry
trichomoniasis is not common in turkeys and chickens. Outbreaks usually occur in warm
climates or during warm weather.
- Etiology
- The etiological agent of trichomoniasis is Trichomonas gallinae (Tg). Tg
is a pear-shaped flagellated protozoan with 4 anterior flagella and an undulating membrane
to provide motility.
- The life cycle of Tg is very simple; it divides by longitudinal binary fission.
- Transmission
- Nearly all pigeons are carriers of Tg. The pathogenicity of the different strains of Tg
is very variable. Adult pigeons transfer the organism to squabs via the "pigeon
milk".
- Raptors often contract trichomoniasis by eating infected pigeons and doves.
- Turkeys and chickens contract the disease by drinking stagnant surface water containing T.
gallinae . Pigeons are believed to be the most common vector by which the water
supplies are contaminated.
- Clinical signs
- Affected birds may have difficulty closing their mouths and may drool and make repeated
swallowing movements.
- Severely affected birds will stop eating, become depressed, ruffled in appearance, and
emaciated before death.
- Lesions
- Lesions are seen in the mouth, sinuses, pharynx, esophagus, crop, and proventriculus.
- Typical lesions are white to yellow plaques or raised masses.
- Diagnosis
- Gross lesions are very suggestive of trichomoniasis but are not unlike those seen with
visceral pox, candidiasis, and hypovitaminosis A.
- histopathology of the lesions will help distinguish trichomoniasis from the above
diseases.
- The presence of large numbers of trichomonads in the oral fluids is usually considered
confirmatory. A wet mount of fresh oral fluids will reveal the motile trichomonads when
examined microscopically.
- Prevention
- Eliminate any carrier birds as they will contaminate the waterers with Tg.
- Provide clean fresh water and eliminate sources of stagnant water.
- Avoid contact between pigeons and doves and susceptible poultry.
- A low preventative level of protozoacide can be fed in the ration or in the drinking
water. Agents that have been used are dimetridazole (Emtryl), nithiazide (Hepzide) and
Enheptin.
- Treatment
- Several drugs have been used to treat trichomoniasis including Emtryl (dimetridazole),
aminonitrothiazole, and Enheptin. These drugs are no longer available for use in the
U.S.A.
- Back yard flocks or pigeons not used for food production may be effectively treated with
dimetridazole by prescription of a veterinarian (1000 mg/L in drinking water for 5-7
days).
- Other avian protozoal diseases seen in gallinaceous birds include Leucocytozoonosis, Cryptosporidiosis, and Hexamitiasis ( Hexamita
meleagridis ).
