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Understanding Herpes
Virus in Pigeons
Dave Rupiper DVM
Kenneth T. Briggs DVM, PhD
Herpes virus, also known as Infectious Catarrh, is a a contagious, persistent
virus causing respiratory and neurologic disease in pigeons. In its breadth of clinical
signs, occasional virulence and persistence in carrier birds, Herpes infections
of pigeons somewhat resembles diseases caused by similar Herpes species in other
domestic animals. (Fortunately, Herpes infections are very specific to their natural
hosts -- we can't infect our birds with our varieties, nor can we contract the pigeon
forms!) Birds having Herpes infections are often concurrently infected with Mycoplasma,
Chlamydia (Psittacosis/Ornithosis) and bacteria.1 As a result, signs of disease
may not always be straightforward. Herpes virus was first identified in pigeons
in the U.S. in 1945 and in other countries during the next 40 years.2 Multiple types
of Herpes virus affect other species such as raptors, waterfowl, psittacines and
poultry.2,3
Herpes virus in pigeons may be of two or three different forms. The most common
form, Pigeon Herpes Virus (PHV), may cause mild respiratory and liver diseases.
Two strains of PHV have been isolated, mild and severe PHV.4
The second form, Pigeon Herpes Encephalomyelitis Virus (PHEV), may cause paralysis,
torticollis (twisted necks and rolling) and other neurologic signs without causing
respiratory signs, making it difficult to distinguish between PHEV and Paramyxovirus.
Fortunately, PHEV has not been reported to be a significant problem in the U.S.
but may be observed in birds imported from the Middle East.
The third reported form of PHV causes inflammation of the cloaca and vent but the
distinctiveness of this form has not been confirmed.2
Etiology (Cause) and Transmission: Herpes virus belongs to a group of DNA viruses
known as the Herpeviridae which includes the viruses which cause Marek's Disease
of poultry, Duck Plague, psittacine Pacheco's disease, and Infectious Laryngotracheitis
of chickens.5 PHV is usually passed from affected adults to squabs during feeding.
It can be transmitted by nasal discharge as well as in saliva, feces and urine.
In most flocks, PHV is already present but birds only manifest signs if the strain
is severe, as with PHEV, or the birds are stressed by management problems and concurrent
diseases.
Signs: PHV causes upper respiratory signs. These include reddening of the eye, cere
and lids, nasal discharges, graying and filming of the mouth and oral cavity, and
occasionally open-mouthed breathing. These respiratory signs and discharges are
referred to as "catarrh." Other symptoms include fluffed posture, depression,
diarrhea, weakness during flight and anorexia.
PHEV causes neurological signs such as paresis ( muscle weakness), paralysis, circling,
seizures and twisted necks. PHEV is also much more severe than PHV and may result
in rapid and high mortality within a loft.
Diagnosis: The classic diphtheritic (filmy slime in the mouth) upper respiratory
signs are fairly diagnostic for PHV but may be confused with the "Ornithose
Complex" involving concurrent infections of Mycoplasma and Chlamydia. Diagnosis
is most easily achieved via necropsy (autopsy) of an affected bird. Special staining
of the spleen and liver allows a pathologist to identify special inclusions within
the cells which are called "intranuclear inclusion bodies" or "INI
bodies." The liver and spleen often have tissues damaged with PHV.
Treatment: There is no cure for the disease and only through improved management
can we hope to achieve control.6 Treatment with a drug called acyclovir may help
control severe signs but the disease often returns if the medication is discontinued.
It is best to allow Herpes virus to run its course and let the birds develop a natural
immunity. Passive immunity (antibodies are transferred from parents to squabs in
"crop milk") protects the young until weaned. Isolation of obviously affected
birds is recommended since they are often infected with other contagious diseases
as well.
Prevention: Killed and live virus vaccines have been formulated, but these only
prevent shedding and dissemination of the virus from affected birds. Vaccines do
not prevent pigeons from being carriers of Herpes virus.2,5 Natural infection of
mild strains with subsequent immunity is still the best method to protect a flock
from virulent strains of PHV.2
Like so many diseases of our birds, prevention and treatment often depend on cleanliness,
good husbandry, good nutrition and preventing overcrowding. The days of keeping
six inches of dry litter on the loft floor to prevent disease are gone, just as
using NFZ to control canker and Paratyphoid is obsolete. Intense competition at
shows, performance flying of young birds and increased production of squabs are placing
more demands on the fancier in order to still be competitive. The key to success
is educating ourselves about the disease process and by progressive management of
our lofts.
References
1. Schrag L: Healthy Pigeons, 6th English Revised Ed, Hengersberg, W Germany,
Schober Verlags-GmbH, 1989, pp 48-53.
2. Tudor DC: Pigeon Health and Disease, Ames, IA, IA St Univ Press, 1991, pp 34-38.
3. Fraser CM (Ed): Part VI, Diseases of Poultry. in Merck Veterinary Manual 6th
Ed, Rahway, NJ, Merck & Co., Inc., 1986, p 1272.
4. Kaleta EF: A Selection of Disease Syndromes in Pigeons. Proc 1st Conf European
Comm AAV, 1991, pp 77-81.
5. Dorrestein GM: Viral Infections in Racing Pigeons. Proc AAV, 1991, pp 244- 257.
6. Marshall R: Management of Pigeon Diseases. Proc AAV, 1990, pp 122-135.
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