peace
misha
>>>>>>>>>>>>>>>>>>>>>
EXSANGUINATION, BOVINE, BY MOSQUITOES - USA (LOUISIANA) (02)
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ProMED-mail post
[1]
[We had had a suggestion that the Louisiana cattlemen should have put
impregnated ear tags on their cattle to prevent this condition ...
[but] the cattle already have impregnated eartags to control fly
bothering and the losses attendant on attempting to round up and
insert new eartags in the summer heat ... so I passed it to my friend
Dayton Steelman in Lafayette for comment. One of the references quoted
was:
Focks D A. McLaughlin R E. Nasci R S.
"Effect of permethrin treatment of cattle on Psorophora columbiae
populations: preliminary field test of a host management concept." J
Am Mosq Control Assoc 7(1):1-6 1991
Attempt to control _P. columbiae populations_ by application of
permethrin to their preferred host cattle. Authors concluded that host
abundance was more important than mosquito abundance & that the
treatments by a course spray reduced mosquito abundance by some 83%.
(13 refs) - Mod.MHJ]
***
[2]
Date: Tue, 29 Sep 1998 09:51:24 -0500
From: Dayton Steelman <dsteelm@comp.uark.edu>
In my opinion the best job against mosquitoes is by far "large area
treatment" of ULV insecticides --I really mean Ultra Low Volume. Like
around 1-2 fl.oz. per acre applied by an airplane or by ground
equipment with the proper equipment to break the chemicals up into
around 10 micron size droplets for the ground equipment and 50-100
microns for the airplane. Putting the chemicals out and letting the
prevailing wind drift the insecticide across the cattle does an
excellent job and can be repeated day and night if necessary. It kills
the adults on the animals, resting in various vegetation and while
flying.
The very best example of this was the VEE control program by the USDA
in the early 70s. After two applications of airplane application of
malathion and dibrom there were no measurable numbers of mosquitoes
left around the cattle or human areas. Groud application equipment can
be mounted on a small trailer or pick/up and driven on the upwind side
of the animals at about 15 miles per hour even in pastures --can be
placed in a boat and driven along canals etc.
I think eartags would kill lots of mosquitoes --but they have to land
on the animal and attempt to or actually feed before the insecticide
knocks them down or kills them --some chemicals take about 6-8 hours
or longer to kill treated mosquitoes...
- ---
Dayton
UA, Fayetteville
***
[3]
[Earlier Dayton had commented on the initial posting:]
Date: Thu, 24 Sep 1998 15:13:37 -0500
From: Dayton Steelman <dsteelm@comp.uark.edu>
Been there and seen that! I got to LS and U in the summer of 1965 and
heard all about the earlier "monster" hoards of mosquitoes -- and yes
they were _Ae. sollicitans_ -- that and the next 2-3 years caused the
pressure to be placed to hire someone to conduct research to help
solve this kind of problem. Lucky for me I got the job. In 1971 at
just about exactly the same time that VEE moved from Mexico into
Texas, we were in the middle of quite similar "monster hoards" of _Ae.
sollicitans_ attack. On several occasions I went with local
veterinarians to watch them post dead cattle -- and what you describe
was the same things we saw.
However, in some cases we found upon
observing the respiration system beginning in the nostrils that they
were completely blocked by adult female mosquitoes and -- we thought
that as you stated the animals were in a super-stressed or shock
condition and could not muster the strength to "snort" out the
mosquitoes they were breathing into the respiration system!
The bottom line was the VEE spray progam provided by USDA to protect
horses for the 14 days necessary for the VEE vaccine to take effect
actually convinced the human population in the state that something
could be done to protect humans and animals from mosquito attack ---
due to that I helped start Mosquito Abatement Districts in the
Parishes of Calcasieu, Cameron, Jeff Davis,within the next 2-3 years
and later, East Baton Rouge, St. Tammany, St. Charles, Iberia, Caddo,
and at Monroe.
Why have the Mosquito Abatement Districts in the area not been
actively fighting the problem?
- ---
Dayton
***
[4]
[In internal discussions on this posting, Charlie Calisher said that
he had seen the same as Dayton but in Florida. "In 1967, on a trip to
Everglades National Park with Dan Sudia, we came across an
exsanguinated cow in a cane field. The owner told us the cow had
appeared in good health the previous day but that that evening he had
seen "more mosquitoes than I have ever seen" come up out of a pond and
attack the poor creature. Bled it out. No matter how much blood a cow
can have, a zillion mosquitoes can take damn near all of it. I asked
Carl Mitchell how much blood does a mosquito take in a blood meal. He
said 5-6 ul. Thus, 5 ul x 1000 mosq = 1 ml and 1,000,000 mosquitoes
would take a L. Doesn't sound as though exsanguination is the answer,
although it might be. More likely, Carl says and which you had
suggested, suffocation is the answer." Or exhaustion and shock. For us
it was interesting that they demonstrated a terminal bacillary
bacteraemia. These were never _B. anthracis_. We did check one isolate
out completely and it was _B. megaterium_. Mod MHJ]
[Other estimates are that a mosquito blood meal is only 2.5 ul,
requiring 2 million feeds to drain 1 liter of blood. Since Martin
calculates that a Louisiana bull has some 45 l. of blood in it, to
knock its hematocrit down fatally by 70% would require 60 million
mosquitoes to feed on it in a couple of days. Perhaps the bites
promote internal hemorrhage, although this was not mentioned in the
autopsy reports - Mod.JW]
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