During the summer of 1994, an outbreak of disease resulted in the rapid death of over 1000 breeding pheasants at a game farm with approximately 7000 birds. This was caused by a type of ‘coronavirus’ that is distinctly different from the respiratory coronavirus of birds known as ‘Infectious Bronchitis’.
All birds are susceptible, but the most severely affected are young birds. However, the majority of cases are seen in breeder birds.
ACUTE symptoms: sudden mortality (as high as 50%), decreased food intake and white diarrhoea.
CHRONIC symptoms: sneezing, decreased egg production and reduced hatchability.
Post mortem examination will show;
pale, swollen kidneys
visceral gout may be seen in some birds
PCR on affected tissue/ respiratory tract will determine infection.
Targeted antibiotic therapy using culture and sensitivity may help control secondary infections but will not help birds recover from the virus itself.
Supportive electrolytes through the water will help birds keep rehydrated and so have a greater chance at recovery.
Prevention and Control
Routine cleaning and disinfection; The virus can be easily destroyed by heat, lipid solvents, nonionic detergents, formaldehyde, oxidizing agents and UV irradiation. 1% solution of formalin & 0.5% peracetic acid seems to be effective.
Vaccination either in the water or by eye-drop. The vaccines available are designed for use in chickens so are used off license.
Biosecurity between houses; footdips, changes of clothing/ footwear will help reduce spread between different groups of birds as the virus spreads by airway secretions and faecal contact.
Optimising the birds environment will help reduce spread and decrease stress;
Reducing stocking densities (specifically assess the male:female ratio in breeder pens).
Ensuring birds have adequate access to food and a clean water supply (including sanitisation – ie. hydrogen peroxide, chlorine etc).
Ventilation; Controlling ammonia levels within the housing.
Using appropriate shed temperatures
Looking for and controlling any pre-existing diseases; like Coccidiosis
Coccidia is a protozoal disease. Despite there being many different strains of this protozoa each individual one is very species specific. This means that pheasant coccidia strains will not infect partridges and vice versa.
Strains involved: E. colchici, E.duodenalis, E. megalostoma, E. pacifica, E. phasiani
Inappetence or anorexia
Depression, ruffled feathers, hunching
Poor weight gain
Dehydration & death
Red Legged partridge are more severely affected than grey partridge.
Strains involved: E. caucasica, E. procera, E. koifoidi, E. legionensis
Microscopy: intestinal scrapes inspected under the microscope to identify coccidial oocysts.
Faecal oocyst count: oocyst flotation from a pooled sample of faeces.
Toltrazuril for two days (Baycox, Zorabel)
Amprolium for seven days (Coccibal, Amproline)
In severe cases, this may require concurrent antibiotic therapy to settle a bad dysbacteriosis.
Coccidiostats in feed:
These products help birds to develop natural immunity to coccidia as they age. The drugs restrict coccidia metabolism so that only a low level is maintained in the birds. Therefore immunity is generated more swiftly without the catastrophic damage a clinical outbreak can have on bird growth and wellbeing.
However, in time the resident population of coccidia on a site will become resistant to the coccidiostat and will no longer have an effect. There is only one licensed coccidiostat drug for game birds, Lasolocid acid (Avatec).
Rotating paddocks/fields or where housing is placed. Coccidia is a very resilient parasite and will survive for over a year in soil and in housing. Turning the soil can also help.
Thorough cleaning and disinfection of housing with a product that specifies action against coccidial oocysts (as most products will have no effect):
Power wash all dirt and dust off equipment and housing.
Use a detergent to wash the remaining muck off, pay particular attention to gaps and hard to reach places.
Allow equipment to dry before applying the disinfectant.
Use a disinfectant to cover all equipment and housing and allow for contact time as advised on bottle, eg. Interkokask or Bi-OO-cyst.
Hexamita & Trichomonas
A motile protozoa otherwise known as ‘Spironucleus’. Found in the caecum and small intestine of pheasants and partridges.
A family of protozoa that resides in the caeca of many avian species.
Overgrowth of these motile protozoal species will cause disease in birds.
Depressed with ruffled feathers.
Weakness with eventual death. Mortality can be as high as 80% in birds younger than 10 weeks old.
Identification of small oval undulating organisms from fresh intestinal scrapes under microscope.
‘Emtryl’ was the only treatment available however it is now illegal to be in possession of this drug with intention to administer to game birds.
Birds lose many electrolytes through the diarrhoea process. Supportive therapy with electrolytes in the water is recommended to increase survival rates.
Antibiotic therapy has been used to help control this disease however the exact reason for this is under investigation.
Ensure feed and water systems are contained, covered and hygienic.
Water sanitisation with a suitable product (hydrogen peroxide or chlorine) will reduce the likelihood of shared drinkers being a source of infection for hexamita or trichomonas.
Acidification of water has also been used with success for prevention and control of these diseases.
Overstocked pens are more severely affected due to a combination of increased social stress factors and increased incidence of disease exposure. Reduce stocking densities will help to reduce the severity of the disease in the flock.
Good biosecurity between different groups of birds; change of footwear and separate equipment between houses.