AI Not Detected, Symptoms No Longer Specific

Jakarta, Kompas – Mutation of Avian Influenza viruses which had infected poultry in Indonesia since 2003 has created new problems. AI infected poultry are now no longer showing specific disease symptoms, making it more difficult to detect the disease. Thus was a statement made last week in Yogyakarta by Charles Rangga Tabbu, a poultry disease expert form Gajah Mada University, who is also member of the expert panel of the National Committee on Avian Influenza Control and Pandemic Influenza Preparedness (Komnas FBPI). According to Charles, the new problem of AI in Indonesia is that disease symptoms are now different from those in 2003. So are the tissue damages in infected poultry.

“We’ve experienced difficulties in diagnosing avian influenza in poultry at field. Previously, AI infected birds were easily identified, but now it is not,” said Charles, who is also chairman of the Indonesia Poultry Veterinarian Association. The symptoms of subclinical AI are hard to identify and not specific.
Charles stated that the disease could not be detected with the naked eye or through necropsy. “We need to do laboratory examinations,” said Charles, also a pathology professor at the Faculty of Veterinary Medicine in Gajah Mada University.
A similar statement was said on Sunday (11/1) by I Wayan Teguh Wibawan, Dean of the Faculty of Veterinary Medicine in Bogor Agricultural University (IPB). “Clinical and pathological signs of avian influenza in poultry, especially chickens, are becoming more difficult to diagnose because of the high variation, both in commercial breed and non-commercial breed chickens,” he said.
According to Wayan, clinical signs such as the bluish discoloration of the comb, leg and feet, are no longer guaranteed to appear. “Moreover if the mortality was low, it could be misdiagnosed. People would be confused, is it ND or AI,” he said.
Changes in the disease symptoms could have occurred because of virus mutation or because vaccinated birds were exposed to viruses. The not too strong antibodies allowed the virus to stay in the bird and virus was shed through the bird’s feces.
“We always need laboratory assistance to detect or isolate the virus or by gene or virus amplification techniques,” he explained.
Now, the only clinical signs left are hemorrhages on organs such as kidneys and intestines. The problem is organ hemorrhaging is also found in other poultry diseases, such as Newcastle Disease, cholera, and infectious bursal disease (IBD).
“This is the art of diagnosis by considering its epidemiological aspect, pathological aspect, the chicken’s health history before it became ill, vaccines given, and PCR testing,” he said.
Characteristic similarity
According to Charles, for vaccination to be effective, we need to find similarities in the biological characteristics and matching genetic composition. The strain and subtype of vaccine seed viruses must be homolog with field viruses.
For example, AI virus groups from Purwakarta and Sukabumi are different from all vaccines available in Indonesia. That is because the antigenicity of these groups are different from the two other virus groups in Indonesia, which are the classic Legok group and South Sulawesi group.
Ad Interim Director of Animal Health from the Ministry of Agriculture, Turni Rusli, said that virus mutation is possible. Therefore, to anticipate it the government has conducted early detection programs, for example collaborating with the general public to conduct rapid responses on historical or new information about AI cases.
“If there was information of AI in a certain village, our officers will immediately go to the village, conduct depopulation and targeted vaccination,” he said.
Besides antibodies, birds also have cellular immunity which affects the exhibited clinical signs. But that doesn’t mean there is virus mutation.
“There is a possibility for this to happen because the AI viruses that infected the chicken do not 100 percent match with the bird’s antibody, including antibodies developed from vaccination,” said Wibawan.
The manifestation of subclinical illness is AI viruses could be detected and isolated from healthy-looking chickens. “This is of our concern because the viruses are virulent,” he said.
In response to this issue, Minister of Health, Siti Fadilah Supari said that avian influenza control in poultry must be strongly continued by the Ministry of Agriculture.
According to the minister, after a press conference regarding the Ministry’s program for 2009 yesterday, the Ministry of Health have improved the facilities in 100 AI reference hospitals, two national AI reference laboratories (the National Institute of Health Research and Development and the Eijkman Institute), 8 regional laboratories, and 34 subregional laboratories.
Besides that, the Ministry of Health also distributes oseltamivir to government health offices, AI reference hospitals, district/municipal general hospitals, private hospitals that had treated AI cases, and community health centers in all provinces in Indonesia. (MAS/EVY)
Source: Kompas