No vaccine? Keep up immunity

The World Health Or­ga­nization’s statistics for 2008 point to bird flu incidence in separate parts of the planet. Epidemiologists believe the virus’s active mutations can result in the appearance of a formidable strain that will be lethal also to man. Bird flu is caused by Influenza A virus and its most pathogenic strain is H5N1. It causes a medium- or short-term lethal disease. This virus is carried by migrant birds, primarily wild geese, ducks, terns, herons, seagulls, and some others. Recent studies (South Africa, Turkey, Hong Kong, 2002) show that man’s closest neighbors, sparrows, can also be carriers of this virus. Since then bird flu epidemics have been registered among marine mammals, such as seals and whales, and domesticated animals (pigs and horses).

The first case of bird flu was recorded in the early 20th century in Italy. Since 2003 periodic outbreaks have been registered in China, Japan, Korea, Great Britain, Sweden, Romania, Croatia, Russia, and Ukraine.

MULTIFACED VIRUS

Man can contract bird flu, or avian influenza, through contact with sick birds or by eating them. There are no registered cases of this virus being transmitted between people, but scientists do not rule out the possibility (due to the active mutation of this virus).

The first case of a human being contracting bird flue was registered in Hong Kong in 1997: it was ascertained then that it could be transmitted directly from sick birds to people. Out of 18 people (nine adults and nine children) that were hospitalized, five adults and one child died. Similar cases were recorded in Holland, China, and Vietnam.

After the death of a little boy in Hong Kong in 1999 they started speaking about a new, extremely dangerous strain of the virus. The boy’s first postmortem diagnosis was pneumonia, but further study revealed that he had been infected with influenza virus A. It also transpired that the boy had been in contact with virus-carrying chickens. This was the first documented case of a human being affected by virus H5N1.

Since 2002 cases of bird flu contracted by people (totaling more than 387, with two-thirds having lethal outcomes) have been registered in Azerbaijan, Egypt, Turkey, Great Britain, Hungary, the Czech Republic, and Russia.

Ukraine is also in the risk group. The first case of bird flu was registered in the Crimea in 2005 and other cases were registered in Kherson, Odesa, and Sumy oblasts. In January 2008, bird flu struck two poultry farms in the Crimea. This virus is the biggest threat to poultry and the population in the areas frequented by largest number of migrant birds (the Black Sea and Sea of Azov coasts, Dnipro water reservoirs, Desna and Prypiat estuaries, Shatsk Lakes, and adjacent territories).

MAGIC VACCINE

Scientists all over the world are racking their brains to develop a vaccine against bird flu affecting humans. There are the first positive results. A team at the University of Maryland, led by Daniel Perez, a UM associate professor and virologist, has developed a vaccine component that can be used to immunize both birds and mammals from dangerous forms of the flu, including the highly lethal H5N1 avian influenza strain. Their discovery may well serve to further improve this medicine, although a lot of their colleagues are cautious about this kind of experimenting because this vaccine does not fully conform to the circulating virus and may speed up its mutation.

David Nabarro, Senior UN System Coordinator for Avian and Human Influenza, says: “The biggest problem in developing vaccines is in detecting the virus genome that is uniform for various strains. Vaccines developed on the basis of this genetic data can combat any pathogenic forms. Despite this, I cannot say with certainty how successful they will be.”

In 2008 Russian scientists also claimed to have developed a vaccine against human bird flu. At present a research center’s team in the Russian Academy of Medical Sciences has completed the first round of clinical tests. In accordance with their findings, this vaccine has been recognized as immunogenic-in other words, capable of mobilizing the human system’s immune defenses. However, since there are several kinds of this vaccine, it will be some time before the researchers can determine which kind is the most effective, and most importantly, the safest one.

NO CURE-ALL SO FAR

Tests have shown that some antiviral agents used in human therapy also have positive results when administered to poultry. In Ukraine a team of experts with the open joint stock company InterKhim (Odesa) developed a special veterinary amixin based on amixin IC used to treat human viral infections. According to the findings of the Institute for Experimental and Clinical Veterinary Medicine, this an­ti­viral agent stimulates the production of interferons (natural proteins produced by the body to inhibit virus reproduction) and normalizes the birds’ weakened immune response by stimulating it with B-lymphocytes.

The staff of the Odesa Zoo has appreciated veterinary amixin as an antiviral agent for various groups of birds. “In February 2008, for two weeks we gave injections of veterinary amixin to our birds as preventive therapy. The importance of this preventive therapy is hard to overestimate; during the winter our birds are kept in the same compartment (the only one we have), which is specially equipped for wintering. Na­tu­rally, it means a dense population of zoo inmates; this also means a high risk of viral infections. This is precisely why the application of immunomodulatory drugs is perhaps the only way to avoid serious losses,” says the zoo’s leading veterinarian Dr. Oleksandr Shvets.

This situation cannot be ignored. It appears that now we have a real opportunity to combat the dangerous virus.