Tuesday, June 15, 2010

Team Working on Encephalitis Outbreak

It is with great pride that I bid farewell to Oscar, Alonso and Celestino this morning. They left with Jeremy Ledermann of the CDC and scientists from the Animal Health lab of the Agriculture Ministry (MIDA) to help collect samples in eastern Panama.

Here in Panama, the rumors have gotten ahead of the scientific facts, but I got the straight skinny from the Alex Martinez, my colleague and head of virology at the Gorgas. Basically, there appears to be an outbreak of either Venezuelan or Eastern Equine Encephalitis. One girl, nearly the same age as my daughter, has already died, and many horses have died.

The team is currently near Tortí and will move from there to the Metetí area. We'll be providing the Gorgas will all of the diagnostic samples. There are claims of dead birds in the area, but I should caution that there's lots of mis-information out there in a population that has been historically marginalized and is quite reasonably quite afraid.

STRI's role in this research is multi-faceted. Jose Loaiza will return from defending his PhD in medical entomology from McGill University and will identify the mosquitos collected. They will be then screened for virus, which we hope to sequence in order to tell us where the virus comes from. Blood serum samples from birds in the affected area will be screen for VEE and EEE antibodies. Together we will put this information together to try to understand the ecology of this outbreak. This is quite important because "migratory birds" were immediately blamed for the disease.

Typically, when an outbreak occurs, the conventional wisdom is that the virus was carried into the region somehow. Birds, especially migratory birds, are a convenient scapegoat. However, it may be that the virus has historically persisted as in a local reservoir. Hopefully with the combined study of the small rodent populations (sampling being done by MIDA) and the bird and mosquito populations (our group), we will be able to identify which animal species are part of the transmission cycle.

This is one of the strongest arguments for why we return to the same region year after year to collect specimens. Tissues from museum specimens provide a very useful source of information about the baseline conditions. Had we sampled previously in Metetí and Tortí, we would be able to evaluate changes in the serological condition of birds collected before the outbreak to those collected during and after the outbreak. Thanks to our CDC funded work in the Panama Canal watershed, we will have this baseline information for the center part of our country.

Thursday, January 14, 2010

Updates on the Escudo Hummingbird Question

The new year starts with an intern, Andrea Baquero, who hails from Colombia working in the lab with me. This week we began to collect nuclear DNA fragments from Amazilia hummingbirds (tzacatl on the mainland and Isla Colon) and handleyi (Isla Escudo) to get a more robust estimate of divergence time and gene flow between Escudo and the mainland. We haven't analyzed the preliminary data yet, but the few sequences that I've seen give me the general impression that gene flow was ceased between Escudo and the mainland for some time now.

I have to say that I'm pretty surprised at the level of DNA polymorphism in the Escudo population. Polymorphism is another word for genetic diversity, and as everyone remembers from high school biology, small inbred populations lose genetic diversity overtime due to genetic drift. However, we only have two small nuclear DNA fragments (as opposed to the mitochondrial DNA fragments I discussed earlier) and so this may be a consequence of chance. We will be collecting more data in the coming weeks, and I'll post an update.

I believe that this would make the Escudo Hummingbird, among all the world's hummingbirds, the species with the smallest range.