Swine flu review - News Focus Changes on the farm may be...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
One of the first signs of trouble was a barking cough that resounded through a North Carolina farm in August 1998. Every pig in an operation of 2400 animals sickened, with symptoms similar to those caused by the human flu: high fever, poor appetite, and lethargy. Pregnant sows were hit hardest, and almost 10% aborted their litters, says veterinary virologist Gene Erickson of the Rollins Animal Disease Diagnostic Laboratory in Raleigh. Many piglets that survived in utero were later born small and weak, and some 50 sows died. The culprit, a new strain of swine in- fluenza to which the animals had little im- munity, left veterinarians and virologists alike puzzled. Although related flu strains in birds, humans, and pigs outside North America constantly evolve, only one in- fluenza subtype had sickened North American pigs since 1930. That spell was suddenly broken about 4 years ago, and a quick succession of new flu viruses has been sweeping through North America’s 100 mil- lion pigs ever since. This winter, for exam- ple, up to 15% of the 4- to 7-week-old piglets on a large Minnesota farm died, even though their mothers had been vaccinated against swine flu, says veterinary pathologist Kurt Rossow of the University of Minnesota, Twin Cities. It seems that after years of stability, the North American swine flu virus has jumped onto an evolutionary fast track, churning out variants every year. Changes in animal husbandry, including increased vaccination, may be spurring this evolu- tionary surge. And researchers say that the resulting slew of dramatically different swine flu viruses could spell danger for humans, too. The evolving swine flu “in- creases the likelihood that a novel virus will arise that is transmissible among hu- mans,” says Richard Webby, a molecular virologist at St. Jude Children’s Research Hospital in Memphis, Tennessee. Because people have no immunity to many viruses from other species, strains that on rare occasions leap the species bar- rier can have deadly consequences (see sidebar, p. 1504). And pigs are considered “mixing vessels” in which swine, avian, and human influenza viruses mix and match. Scientists believe, for example, that the last two flu pandemics, or worldwide epidemics, in 1957 and 1968, occurred when avian flu and human flu viruses swapped genes in pigs, creating a new, hy- brid virus that then spread to humans. In each case, the new virus appeared first in Southeast Asia, then around the globe. The 1918 “Spanish flu,” which claimed upward of 40 million lives, may also have arisen first in pigs. “We used to think that the only important source of genetic change in swine influenza was in Southeast Asia,” says Christopher Olsen, a molecular virol- ogist at the University of Wisconsin (UW), Madison. Now “we need to look in our own backyard for where the next pandemic may appear.” Fortunately, the new pig strains that have appeared in North America so far do not ap- pear to readily infect humans. But re-
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/12/2011 for the course BIO 620 taught by Professor Hardy during the Spring '11 term at University of Florida.

Page1 / 3

Swine flu review - News Focus Changes on the farm may be...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online