Mosquito Considerations
In an October 2008 seminar, Dr. Tom Nelson made much of the increased numbers of tropical storms hitting the Gulf Basin in the past several years since Hurricane Katrina. His thesis is that more storms equals more rain, equals more flooding, equals more mosquitoes. This was not much accepted as an explanation for the increased numbers of heartworm cases, as his audience was drawn from the banks of the Mississippi River and from reclaimed swampland. These areas have always had enormous mosquito populations.
The mosquito population may be changing. The researchers at our seminar expressed great frustration over the fact that there is NO DATA readily available (possibly not even in existence) about the numbers of mosquitoes, the population density of mosquitoes, the species ratio of mosquitoes, or the percentage of mosquitoes carrying microfilariae.
The Asian Tiger mosquito, Aedes albopictus, has displaced Aedes aegypti in some locations. It is a much more aggressive mosquito, and it bites in daytime as well as nighttime. It can survive winters as far north as Toronto, Canada. It would be of interest to know whether the population of Aedes albopictus has burgeoned in our area, but I haven't been able to get any data from ag extension.
More mosquito bites equals more potential filaria infection. The research guys made reference to the preventive medicine being “overwhelmed” by huge numbers of microfilariae. Interestingly, they don’t recommend bigger doses of medication or more frequent dosing as effective strategies to deal with this ostensible “overwhelm”.
In 1978, I worked for a veterinarian in Pocahontas, Arkansas. We were situated between the Black River bottom and the Current River bottom, with rice fields in the middle. Horses in this low-lying flatland would run all night to escape the mosquitoes. [Researchers at LSU have documented horses there receiving 1,000 mosquito bites per hour.] My employer moved from his home adjacent to the clinic into the foothills on the other side of town. With daily heartworm preventive, he still could not keep all of his own dogs free of the parasite.
As bad as our mosquitoes are here, they were dramatically worse in that environment. We do have more rice-farming in our area now, and there are lots of folks who feel that the mosquitoes are worse than in years past, even in town. However, there are no hard numbers to work with. Subjectively, I can't say myself that the mosquitoes are noticeably worse now than five years ago.
How frightening. I live in downtown Memphis directly on the Mississippi River. I know of two families who have both had dogs that acquired heartworms while on "preventative". Because of this and what I've read, I switch between two different drugs. While it probably won't make much difference, I am hoping that the Ivermectin in Heartguard will have some reach back effect if the other fails. Ha!
By the way, I definitely have mosquitos that bite during the day. Scary stuff.
Thanks for the info and for the very interesting blog. I plan to bookmark it and read more.
Posted by: doggiemom | June 02, 2009 at 12:24 AM