What disease is Pigeon Paramyxovirus Type I

Raising pigeons is like raising other poultry: the wider the scale of rearing and the greater the numbers, the more diseases inevitably follow. This disease was discovered in recent years and is a highly contagious, septicemic infectious disease caused by Pigeon Paramyxovirus Type I. It is commonly known as pigeon Newcastle disease, and some also call it pigeon plague. In pigeon flocks it sometimes strikes ferociously, and sometimes occurs only sporadically. Squabs infected with this disease easily die in large numbers, and young pigeons and parent pigeons also die. The incubation period of this disease is 1 to 10 days, usually 1 to 5 days. Before onset, the birds appear completely normal; when mixed together, the virus can be transmitted to @#@247@#@ from different pigeon flocks, causing an outbreak of this disease. The characteristics are diarrhea, tremors, unilateral or bilateral leg paralysis; chronic cases and cases in the late epidemic stage have symptoms of head twisting and neck tilting. The mortality rate is between 20 and 80%, and the general mortality rate can reach over 50%. In late October 1997, a pigeon farm in Zhejiang kept 30,000 pairs of pigeons, of which 500 pairs of breeding pigeons first developed this disease. After interferon treatment, only 2 months later, the disease broke out again in two young pigeon houses. From the adoption of comprehensive prevention and control measures to the control of the disease, the whole process lasted more than 4 months, during which more than 3,000 pairs of parent pigeons and 4,500 young pigeons died of the disease, and more than 5,000 pairs of squabs died. Parent pigeon mortality reached 13%, while the mortality rate of young pigeons (including culled substandard birds) reached over 50%, with direct economic losses of nearly one million yuan. This shows how great the harm of this disease is to the pigeon industry. When pigeons go out for training and flight competitions, placing pigeons from different flocks together in the same vehicle or the same room very easily spreads this disease.

1. Clinical symptoms

At the beginning, sick pigeons are listless, with ruffled feathers, poor appetite, increased thirst, general tremors, watery diarrhea, and stand dully, but can still escape capture. As the disease progresses, sick pigeons close their eyes and hunch their necks, are unwilling to move, completely lose appetite, and the general tremors become increasingly obvious. They often swallow saliva, and the loose droppings change from watery to mostly greenish-white or yellowish-white, especially with the feathers near the cloaca and rear abdomen stained by feces. Most sick pigeons develop neurological symptoms, later developing leg paralysis. Sick pigeons cannot stand and often squat or lie on their sides. When driven, they can only move their bodies by staying close to the ground on the lying side and paddling the ground with the upper foot. During paroxysmal spasms, the pigeon's body muscles tremble, the neck twists or becomes stiff; seeing food, they want to eat but always peck inaccurately and cannot get it into their mouths. They want to walk forward but cannot, and can only circle in place. Some hold their heads backward, some show unilateral leg or wing paralysis, and some stumble when walking. The main neurological symptoms are head shaking, neck twisting, drooping wings, weak legs, circling, and ataxia. A small number of sick pigeons have ophthalmitis, conjunctivitis, and nasal discharge. Finally, they pass thin or pasty foul green droppings and die of exhaustion. The course of disease is 3 to 7 days, but some last more than 10 days. Sick pigeons with a long course of disease are extremely light in weight, and the whole body feathers lack luster. The pigeon body shows extreme exhaustion. At this time, cases with neurological symptoms increase, but in some farms the increase is not obvious.

This disease sometimes shows sudden explosive epidemics, causing large numbers of pigeons to die rapidly, and sometimes occurs slowly, causing continuous sporadic deaths among pigeons. If other diseases occur concurrently, the death losses will increase.

2. Necropsy lesions

Its lesions are roughly the same as those of Newcastle disease. In appearance, most pigeons have sunken eyes; 30 to 40% of sick pigeons have conjunctivitis, hyperemia, hemorrhage, and discharge. The shanks and feet are dry and wrinkled, and the feathers are severely contaminated. During necropsy, the skin is relatively difficult to peel off; after peeling, the muscles appear dry and slightly flushed. The pectoral muscles may be relatively plump, but may also be extremely thin. There is extensive subcutaneous petechial hemorrhage, especially severe in the neck, in colors such as red and purplish red; this is an inherent characteristic lesion. There is edema and pinpoint hemorrhage in the coronary sulcus of the heart, meninges, and brain parenchyma. In some pigeons, the air sac membranes are cloudy, the proventricular papillae bleed obviously, and some form hemorrhagic bands at the junction of the proventriculus and gizzard; some have patchy hyperemia or hemorrhage under the keratinous membrane, and occasionally the proventricular mucosa shows dark red hyperemia. The pancreas has hyperemic spots and unevenly colored marbled streaks. From the duodenum to the rectum, the mucosa all shows hemorrhage; the liver is enlarged with hemorrhagic points and hemorrhagic patches; the spleen is enlarged with congestive patches; the kidneys are pale and enlarged; the lungs mostly show varying degrees of gray hepatization, with partial necrosis at the edges; the skull often has hemorrhagic patches. In some cases, the laryngeal and tracheal mucosa is hyperemic or hemorrhagic, and some contain fluid or caseous material.

3. Prevention and treatment

To prevent this disease, the feeding management of the pigeon flock should be strengthened at ordinary times, feeding nutritionally adequate feed, ensuring the required amounts of nutrients and vitamins, and doing a good job of pigeon house sanitation, reducing stress factors, so as to improve the pigeons' physique and enhance disease resistance. At the same time, veterinary epidemic prevention and other systems within the farm should be established and improved and conscientiously implemented, and practical and feasible immunization programs should be formulated, with regular epidemic monitoring and vaccination. Vaccination is the key effective measure to prevent the occurrence of this disease. Immune effect by upper respiratory tract vaccination is better than wing web or intramuscular vaccination. According to different circumstances, the prevention and treatment methods that can be selected are:

(1) The most effective vaccine is the inactivated Pigeon Paramyxovirus Type I vaccine. This vaccine is injected subcutaneously in the neck, does not produce strong reactions, and provides good immunity after 1 vaccination, and is very safe. Seven days after injection, the pigeon body antibody can rise from 0 to the 25 level by the micro method. If the same vaccination is given again at this time, after 7 days the antibody rises by another 2 titers, reaching the 27 level. Thereafter, vaccinate once about every 6 months. Generally, 0.5 ml is injected per bird at vaccination (for emergency prevention, it is required to inject 1 bird and change 1 needle). Under normal circumstances, young pigeons kept for breeding are vaccinated once at about 1 month of age, and a booster immunization is given again at about 4 months of age before laying begins. Old pigeons can be revaccinated once every 6 to 12 months.

(2) When an epidemic is prevalent, in addition to rapidly revaccinating breeding pigeons that have not been injected or were injected half a year earlier, epidemic prevention work for young pigeons should also be strengthened. Squabs over 5 days of age can be vaccinated with 4 to 8 doses per bird of Newcastle disease strain W vaccine. If breeding use is considered or there is a serious epidemic threat, 0.2 to 0.5 ml per bird of inactivated Pigeon Paramyxovirus Type I vaccine can be injected subcutaneously at the same time.

(3) For pigeon farms where an epidemic has already occurred, emergency vaccination should be carried out as soon as possible, injecting 2 doses per pigeon of inactivated Pigeon Paramyxovirus Type I vaccine; one may even consider simultaneously injecting 8 doses per bird of Newcastle disease strain IV vaccine, which can rapidly control the epidemic and reduce losses. Or injecting the bivalent vaccine produced by the Department of Animal Medicine of South China Agricultural University is more convenient. (4) For farms with outbreaks, in practice we use inactivated tissue vaccine made from typical virus material tissues (developed through a certain procedure using organs such as the kidney, spleen, brain, and liver of diseased pigeons) for emergency immunization, which is the best way to rapidly control the epidemic of this disease; at the same time, it also has relatively good effects for emergency preventive vaccination of pigeon flocks in suspect farms and emergency vaccination of early sick pigeons.

(5) As for attenuated pigeon Newcastle disease vaccine, although it can be used, it is best to use it cautiously in farms with no history of this disease, to prevent its virulence from increasing through continuous circulation in the pigeon body. For attenuated pigeon Newcastle disease vaccine, during an epidemic period, strain N vaccine can be used by intramuscular injection at multiple doses; if strain W vaccine is used, it may cause relatively large reactions in pigeon flocks in the epidemic period or the effect may not be significant. Therefore, whether the effect of using this type of vaccine is ideal depends to a large extent on whether the selected vaccine is appropriate.

At the same time, comprehensive epidemic prevention measures should also be adopted, strengthening routine and epidemic-area isolation, disinfection, and sanitation work. This point is very important. Especially when there is a disease, comprehensive and thorough disinfection should be carried out to prevent pathogen invasion or spread. Specifically, after diagnosis is confirmed, sick pigeons should immediately be isolated and raised separately from healthy pigeons, all dead pigeons should be deeply buried or destroyed at a designated site, and strict comprehensive disinfection should be carried out on pigeon houses and premises.