AvianBirdsFlu.com: key facts about Avian Influenza commonly called Bird Flu that created world health crises rivaled only by Plague and HIV.
Home Page News Virus Pandemic Vaccine Sympotms Links H5N1 Strain Forum	Bird flu The bird flu has spread to the greatest extent on the territory of the USA. The first outbreaks were recorded in 1983-1985 in small chicken-farms and in the markets dealing with a live poultry. Epizootic outbreak began in Pennsylvania in April, 1983. First low pathogenic H5N2 strain, which caused minor indisposition with respiratory symptoms at chickens, drop in egg production and an insignificant death rate of 0-15 per cent, actively mutated and by October, 1983 has been characterized as high pathogenic.. In spite of the precautions, it was impossible to regulate the spread of disease entirely. In July, 1984 the recrudescence of the disease began in Virginia. As a result the mortality amounted up to 17 million birds the economic damage reached $60 million. In 1986 the H5N2 virus reappeared in five north-eastern states of the USA. Research showed that the poultry in 26 out of 44 live poultry markets in New York and in 12 out of 26 markets in New Jersey was contaminated with H5N2 virus of the bird flu. According to the results of virologic and serologic examination, different modifications of the bird flu germs, containing 11 out of 15 known hemagglutinins (H1-7, 9-11, 13) and 8 out of 9 known neuraminidases, were registered in 24 states of the USA (Alexander D.J., 2002). Since 1994 new varieties of influenza viruses have begun to propagate over the country. First they were induced by moderate pathogenic strains, then-by high pathogenic strains with antigenic formula H7N2, sometimes with H7N3. During the examination of 110 markets in New-York and New Jersey, the bird flu virus was detected in 70 per cent of cases, especially there where chickens were sold with ducks and rabbits. At a phylogenetic research a close relationship was determined between the detected viruses and germs, circulating on wildlife birds, what indicated their adaptation to the poultry. In 1988, 1989 and 2002 these germs got in large poultry farms, situated in eight states. In Virginia 4.5 million birds were destroyed (burned, buried, punched). Chickens perished without any clinical signs, turkey cocks were noticed to have respiratory disease and decline of egg-laying capacity. A transport and people, who kept birds, became carriers of the infection. In 2000-2001 there was a breakout of the flu among turkey cocks, caused by the H6N2 strain, which was not accompanied by a mass mortality, but was characterized by respiratory illnesses and a decline of the egg production. In general in 8 states of the USA 195 troubled farms with 126 herds of cattle and 26 stocks of turkey breeders, 14 of broiler poultry and 27 of breeding broiler poultry, and 2 egg-laying stocks (according to S.S.Yakovlev, main specialist of the Department of Veterinary of the Russian Federation Ministry of Agriculture). The last outbreak of the flu in the USA was registered in July, 2002, damages amounted to 80-90 million rubles. Attempts of using inactivated autovaccines and vaccines from heterogeneous strains with a neuraminidase marker for a flu prevention in the south of the country and in Minnesota were successful (Frame D.D. et all, 1996, Halvorson, 2002). In 1994-1995 the bird flu was caused by low pathogenic for chickens H5N2 serotype viruses in Mexico bordering on the USA. 11 states had the trouble. In two years an original low pathogenic virus mutated towards pathogenicity increase and inflicted economic damage to the amount of about $10 million, annually causing acute H5N2 outbreaks from 1997 to 2001.The country was forced to work out a special program of a flu control, based on the specific disease prevention. For the last five years more than 1,2 billion doses of the inactivated and recombinant vaccines were used. (Villareal-Chavez et all, 2002). In Chile the flu had not been registered for a long time, but in May, 2002 a low pathogenic H7N3 strain was extracted from the chickens of one of the two large broiler farms in the country. Just in 2 weeks the low-pathogenic H7N3 strain mutated into high-pathogenic, mass mortality of the livestock began, and the poultry factory was destroyed. In Pakistan the epizooty, which covered 156 from 286 farms, situated in the radius of 100km, began in December, 1994. The 2,2 million birds were stricken with disease, from 51 to 100 per cent of birds perished. The extracted virus was identified as high-pathogenic. A mass vaccination and accepted antiepizootic measures allowed to stop the outbreak of the disease, and since 2001 the country has been considered free from the flu. In Italy 8 outbreaks of the bird flu, caused by the H5N2 strain, were first registered in 1997-1998 and did not inflict serious economic damages. However in 2000 the most serious outbreak of the flu epizooty happened in this country. The first case occurred in March-December, 1999 in the north of Italy. It was caused by a H7N4 strain of a middle pathogenicity, which in several months mutated into high-pathogenic. Subsequently 199 outbreaks were registered: 164 - at the meat-type turkeys, in individual cases - in the turkey parent flocks, meat-type chicken stocks, also in laying stocks, broiler stocks and in 2 flocks of waterfowl. As a result about 13 million birds were stricken with the disease and destroyed on 413 farms located generally in Lombardy. Turkeys and chickens were the most vulnerable, pheasants, Japanese quails, poultry and wild waterfowl suffered from the disease as well. Flu control strategy was based on a mass treatment of inactivated vaccines from the heterogeneous ?7N3 strain and on an intensive program of sulfur monitoring of indicator groups of birds from vaccinated flocks and disease-free farms in the hazard area. At the beginning of 2003 the high-virulent ?7N7 bird flu suddenly appeared in the Netherlands. In 4 months 212 outbreaks were registered in more than 800 poultry farms, and 13.6 million birds were destroyed in connection with this. In the following the flu wa