Diagnosis and Control of Type I Paramyxovirus Infection in American King Pigeons

In recent years, with changes in the rural economic structure, the breeding of American White Feather King Pigeons has gradually developed in our city. From January to May 2002, some King Pigeon farms in Youxian District, Fucheng District, Anxian County, Santai County, and Zitong County of Mianyang City successively experienced outbreaks of a disease characterized by green watery diarrhea, refusal to eat, short disease course, and high mortality, causing serious economic losses to breeders. Based on comprehensive on-site diagnosis (epidemiology, symptoms, necropsy) and laboratory testing, the author confirmed it as pigeon type I paramyxovirus infection. Tissue inactivated vaccine prepared from the liver, spleen, and brain of dead diseased pigeons was used to immunize affected pigeon farms and local pigeon flocks, achieving relatively satisfactory results in controlling the epidemic. Over the past year, the prevalence of this disease in the local area has been basically brought under control. The relevant situation is reported as follows.

I. Epidemic Situation and Symptoms

In late January 2002, pigeon flocks at two breeding households' American White Feather King Pigeon farms in Weicheng Town, Youxian District, and Jiepai Town, Anxian County, Mianyang City, totaling about 3,500 birds (including over 1,400 squabs), successively became ill. The disease struck fiercely and spread rapidly, generally spreading throughout the entire flock in about 7 to 10 days, with an incidence rate as high as 60% to 80%. Sick pigeons showed listlessness, ruffled feathers, and reluctance to move; they refused to eat but increased water intake and passed green watery diarrhea; in the later stage, tremors and unsteady standing appeared, and a small number of sick pigeons (mostly adults) showed neurological symptoms such as head twisting, torticollis, and impaired movement and flight coordination; the disease course was mostly 1 to 5 days, with a few pigeons showing neurological symptoms lasting more than 10 days, and adult pigeon mortality ranging from 30% to 80%; squabs became ill acutely with a short disease course, and most squabs aged 7 to 10 days died suddenly without obvious symptoms, with few remaining of the over 1,400 squabs, and a mortality rate approaching 100%.

It is understood that neither of the above two pigeon farms had ever carried out any immunization, and after the onset of disease they had used norfloxacin, gentamicin, and oxytetracycline for treatment.

By May 2002, more than ten King Pigeon farms in Fucheng District, Santai County, Zitong County, and other areas of Mianyang City had also successively experienced the above epidemic disease.

II. Necropsy

Necropsy was performed on more than 30 dead pigeons, and the relatively consistent lesions were: the carcass appeared mildly dehydrated (sunken eyeballs, shriveled shanks), feathers around the anus were often contaminated with green diarrhea, and there was mucus in the oral cavity; there were obvious patchy purplish-red and black congestive hemorrhagic areas under the skin of the neck; hemorrhagic spots could often be seen on the surface of the cranial bones of the head; most crops contained gas and fluid with a sour odor; the spleen was slightly enlarged with obvious congestion and hemorrhagic spots; the pancreas showed uneven congestion and hemorrhagic spots; the koilin layer of the gizzard was relatively easy to peel off, and streak-like hemorrhages were often present beneath the koilin layer; the intestinal tract (especially the duodenum and rectum) and the cloacal mucosa showed severe hemorrhage. In some sick pigeons, congestion and hemorrhage of the larynx and trachea were visible, with a small number of hemorrhagic spots on the epicardium, and in a few sick pigeons, congestion and hemorrhage of the proventricular mucosa were visible.

No obvious lesions were seen in the liver, kidneys, lungs, thoracic cavity, or abdominal cavity.

III. Laboratory Testing

1. Bacteriological examination: Smears were made from the liver, spleen, and heart blood of dead diseased pigeons; after Gram staining, no bacteria were observed under the microscope; under aseptic operation, the liver, spleen, and brain of dead diseased pigeons were collected and inoculated onto ordinary agar plates and MacConkey medium, and after culture at 37°C for 24 hours, the result was no colony growth.

2. Newcastle disease hemagglutination inhibition test: Blood was collected from the hearts of sick pigeons (16 birds), serum was separated, and the Newcastle disease hemagglutination inhibition antibody titer was determined by the beta micro method. The results showed that varying hemagglutination inhibition antibodies were detected in all, ranging between 2 log2 and 8 log2. Among them, 2 birds had 8 log2, 5 birds had 7 log2, 2 birds had 6 log2, 1 bird had 5 log2, 2 birds had 4 log2, 3 birds had 2 log2, and 1 bird had no detectable antibody.

IV. Control Measures

1. Baidusha was used for comprehensive disinfection of affected pigeon farms (pigeon houses, pigeon body surfaces, equipment, etc.), and dead pigeons were sprayed with disinfectant solution and deeply buried. Baibingxiao was used in drinking water to control secondary bacterial infection; multivitamin electrolytes were added to drinking water to replenish water lost due to diarrhea and regulate the body's electrolyte balance.

2. The brain, liver, and spleen of dead pigeons with typical lesions were collected, normal saline was added in proportion, and after homogenization with a high-speed tissue blender and filtration, they were inactivated with formaldehyde; after passing sterility tests and safety tests, a tissue inactivated vaccine was prepared. A total of about 40,000 milliliters of tissue inactivated vaccine was produced this time, used for emergency immunization of newly affected pigeon farms and preventive vaccination of healthy pigeon farms. For squabs over 10 days old and adult pigeons, each pigeon received 1 milliliter subcutaneously or intramuscularly, repeated once after one week, and then boosted once every six months thereafter. While injecting the tissue inactivated vaccine, Newcastle disease clone 30 or N79 was also administered in drinking water immunization at conventional doses. Affected pigeon farms generally brought the epidemic under control about half a month after emergency immunization and basically returned to normal in about one month, thereby greatly reducing losses on affected farms. Healthy pigeon farms immunized according to the above method also had very good preventive effects. For more than a year, the prevalence of this disease in the local area has been basically brought under control.

V. Discussion

1. From January to May 2002, some King Pigeon farms in Mianyang City experienced a disease characterized by watery green diarrhea, refusal to eat, rapid death, and high mortality. Through epidemiology, symptoms, necropsy, and combined with laboratory test results, the author diagnosed it as pigeon type I paramyxovirus infection.

2. Once type I paramyxovirus infection occurs on a pigeon farm, using tissue inactivated vaccine prepared from the diseased materials of locally obtained dead pigeons with typical lesions, combined with ND clone 30 or N79 live vaccine, for emergency immunization of newly affected pigeon flocks and surrounding threatened areas is an effective way to control this disease.

3. The reliable way to prevent the occurrence of this disease is preventive vaccination. It is recommended to use pigeon type I paramyxovirus oil emulsion inactivated vaccine together with injection of chicken Newcastle disease strain IV (such as N79, clone 30) during preventive vaccination, which can achieve a relatively good preventive effect.