Nepal | July 19, 2019

Avian influenza: Fowl plague

Kedar Karki

The frequency of disease transmission from birds to humans is low, but the very young, the elderly and those with compromised immune system should be cautious. Many of these diseases are transmitted by food contaminated by fecal matter

Bird keepers should be aware that some avian diseases can be transmitted to humans.

It is important to note that such diseases are uncommon and they should not discourage bird keeping. For most people avian diseases do not pose a serious threat but bird keepers should be aware of them and seek medical assistance if necessary.

The infectious agents may be protozoal, fungal, bacterial, chalmydial or viral. Individual susceptibility and seriousness of these various microbial infections vary with age, health status, immune status and whether early therapeutic intervention is sought.

Avian influenza chalmydiosis, salmonellosis and colibacillosis are the most common. Chalmydiosis salmonellosis avian influenza may be serious and life threatening.

Avian influenza type belongs to paramxo viridae. Avian influenza can occur in most if not all species of birds. Avian influenza is categorized as mild or highly pathogenic H5 and H7 virus types that belong to highly pathogenic type.

The mild form produces loss of appetite, respiratory diseases and diarrhea. The highly pathogenic form produces facial swelling blue comb and wattles and dehydration with respiratory distress. Dark red/white spots develop in the legs and combs of chickens.

There can be blood tinged discharge from nostrils. Egg production and hatchability decreases. There can be an increase in production of soft shelled eggs. Avian influenza virus can remain for long periods of time at moderate temperatures and can live indefinitely in frozen materials.

As a result, the disease can be spread through improper disposal of infected carcasses and manure. Avian influenza can spread by contaminated shoes, clothing crate and other equipment. Insects and rodents may mechanically carry the virus from infected to susceptible poultry.

Chalmydia psittaci is an unusual bacteria like organism found worldwide and affects more than 100 avian species. It causes a disease called psittacosis or parrot fever when it occurs in psittacine birds and the disease is called nithosis.

Chalmydiosis is primarily transmitted by inhalation of contaminated fecal dust and is spread by birds which are the main reservoirs for the disease. The organism is excreted in both feces and nasal secretions.

Shedding is sporadic and in usually induced by stress. A carrier state can persist for years. The organism survives by drying which facilitates oral spread and allows transmission on contaminated clothing and equipment. Chalmydiosis can be transmitted to birds from bird feces and birds to humans. Human to human transmission can occur mainly by exposure to saliva.

Chalmydiosis is an occupational hazard for persons working with psittacines and pigeons or people working in turkey slaughter plants and avian diagnostic laboratories. The incubation period of chalmydiosis is 4-15 days although 10 days is most common. In affected birds’ diarrhea, coughing and ocular nasal discharges are common signs.

There may be high mortality if the diseases are unrecognized or untreated. In turkeys there is a drop in egg production. In humans chalmydiosis manifests itself as a feverish respiratory disease. There is usually a sudden onset of chills, muscles and joint pain, headache, cough, loss of appetite and chest pain.

Complications may result from an enlarged spleen, inflammation of the heart muscle and reduced heart beat rate.

There are approximately 200 different serotypes of salmonella species. Most animals are susceptible to salmonella infection. This bacterial infection occurs most frequently in stressed individuals.

Common clinical symptoms in all species include diarrhea, vomiting and a low grade fever. Infections can progress to dehydration weakness and sometimes, especially in the young and very old, death may occur.

The incubation period is 6-72 hours although 12-36 hours is most common. Salmonella is transmitted by ingestion of food contaminated by fecal material. Excretion of bacteria varies from a few days to weeks.

In some instances, typhoid fever infects humans. Salmonella enteriditis in fecal material is able to penetrate egg shells, and may be present in uncooked eggs.

Colibacillosis is caused by escheria coli infection. E. coli is a bacteria which normally inhibits the intestinal tract of all animals. There are a number of strains in many species.

Not all strains are pathogenic. In poultry, E.coli infections may cause septicemia, chronic respiratory diseases, sinusitis, pericardistis and salpingitis.

Humans with colibacillosis usually manifest diarrhea, which may be complicated by other syndromes depending on the e.coli serotype. This complication may include fever, dysentery, shock, and purpura.

The incubation periods are 12 hours to 5days although 12-72 hrs is most common. Transmission is via fecal oral rout. Colibacillosis is often food or water borne.

Bird keepers should be aware that they can contract certain illnesses from birds. The frequency of disease transmission from birds to humans is low, but the very young, the elderly and those with compromised immune system should be cautious.

Many of these diseases are transmitted by food contaminated by fecal matter. Prevention simply involves proper hygienic and sanitation. Wearing a face mask to avoid inhaling bird dust is also recommended.

Karki is M.V.Sc. Preventive Vet. Med, Public Health


A version of this article appears in print on March 22, 2017 of The Himalayan Times.


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