Catching viruses

  • 14/11/1994

Catching viruses IN SEPTEMBER 1993, a new strain of cholera got a grip on India. Within a few weeks, the epidemic floated to the shores of Latin America, the bacteria believed to have been smuggled in via the tainted water of large ballast tanks (which are filled with water to give the ship stability when it is empty of cargo) of ships that arrive at America's eastern shore.

While fearful, new strains of tuberculosis, malaria and aids stalk the Third World, it is the new diseases that breaking out in unexpected places that cast a shadow over the world. The rich nations optimistically believe that they have controlled infectious diseases through better sanitation, nutrition, and medication. This is the right recipe for complacency -- but not for long, as the alarming history of Jacobson's disease shows.

Karyovirus-II (K-II), the causative agent of Jacobson's disease, is a parasite that attacks the megakaryocyte cells (cells that make blood platelets) in the bone marrow. Without these platelets, blood does not clot, rendering the infected person vulnerable to internal haemorrhage or profuse bleeding through open wounds. K-II is spread by mosquitos -- specifically, the Anopheles bengalli. It is also transmitted through the patient's faeces, which discharges live virus.

Notorious record
K-II is believed to have evolved in the lower Brahmaputra valley in southeastern Tibet. The earliest available record of the disease dates back to 1903, when Jacobson -- an army doctor who was in Britain's trade and frontier negotiating team led by Francis Younghusband -- reported the death of 2 British soldiers in the Brahmaputra valley under mysterious circumstances.

The lower Brahmaputra valley was once thickly forested. The extreme temperature of the high mountain ranges protected the passage of mosquitos to inner Assam and Bengal. The disease faced another barrier in the mid-'40s, when Chinese authorities stopped all humans and cattle migration from the valley into Tibet. It was in 1959, when the Chinese annexed Tibet, that the virus is supposed to have slipped into inland China. The brutal trench wars of the Indo-China war in 1962 confirmed the resurgence of the disease.

How K-II got to Brazil is a matter of raging controversy -- but in a world full of globetrotters, it is only natural that the disease will travel, too. Dengue fever was introduced into the tropics in the 18th century by merchant ships; in the late '60s, a monkey from Uganda introduced a new virus into Germany and killed 7 laboratory workers.

Cattle and K-II
The most acceptable explanation for K-II's sidling into South America is that it came through the Sino-Brazilian cattle breeding exchange programme in the '70s. Genetic testing shows that the original strain came from Ningxia, about 1,000 kilometers from Guizou***(where?), where many of the cattle came from. Once the cattle reached Malto Gross in Brazil, Aedes albopictus, a local mosquito, tasted first blood. In turn, Aedes bovii, a cousin of A albopictus, extended its domain to ungulates in the wild. The epidemic had begun.

The policy of clear-felling of forests by timber and paper companies made matter worse. Settlements meant more hosts and the virus spread to the cities of Sao Paulo, Recife and Rio de Janeiro, where it fed on the unhygienic conditions in the slums and shanties. Initially, K-II had a fatality rate of about 10 per cent. But the anti-viral drugs that were used to cure patients produced a killer strain with a mortality of about 50 per cent.

Changes in the environment brought about by human activity and the weather have also caused the disease to spread. For example, a good rainy season in the early '90s in New Mexico led to the harvesting of a bumper onion crop, consumed both by rodents and the area's Native Americans. The crop led to a boom in the population of hantavirus-carrying mice, which infested the people, killing dozens.

In India, however, several such incidents virtually go unnoticed. The early records of the forest department of northern Assam (then under the viceroy of the State of Bengal) mention a rare disease in herbivores and humans. In the '60s, physicians mistook the disease as a form of botulism or shigellosis. Later, when virus enumeration and tests could not confirm a phage infestation, the illness was termed a fever of unknown origin.

Every year between May and June, about 100,000 sheep traverse more than 700 km, starting from eastern Rajasthan -- especially from the districts of Bikaner, Jaisalmer, Barmer, Jodhpur, Churu, Sriganganagar, and Pali -- because of the searing heat and paucity of pasture. The flocks move to the neighbouring states of Haryana, Punjab, Madhya Pradesh and Uttar Pradesh and return only at the onset of the monsoons. The migration brought a disease to some villages in Mandsur and Guna districts. Scientists are unable to identify it but believe that the disease is probably a resistant form of Anthrax. Although the toll has not been alarming, the victims fear that they could be adversely affected in the years to come.

Although the plague epidemic has taken centrestage in India this season, it is now imperative that quarantine laws are made more stringent, applied biotechnology is used to produce vaccines on a massive scale, and a common forum is established for the exchange of information between nations. The onus is not only on the Indian government and ngos, but also on the corporate world, which has to meet its social obligations.

Each step in the success story of a parasite, from oblivion to pandemic proportions, is remarkably simple: the diffusion of people, mixing of species, poverty, war and environmental changes contribute to the rise of a pathogen. The best that humans can do is keep a few paces ahead of the disease through constant monitoring, simple hygiene and some commonsense.

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