[leps-talk] Non-avian vectors and rapid spread of WNV

Grkovich, Alex agrkovich at tmpeng.com
Tue Aug 12 12:24:47 EDT 2003


Mike,

I can't remember ever seeing a Cabbage Butterfly at bird droppings...this is
normally reserved for Limenitis, Satyrids, etc.

Alex

> -----Original Message-----
> From:	Michael Gochfeld [SMTP:gochfeld at EOHSI.RUTGERS.EDU]
> Sent:	Tuesday, August 12, 2003 11:34 AM
> To:	Bob Augustine; leps-l at lists.yale.edu; tils-leps-talk at yahoogroups.com
> Cc:	cdcresponse at ashastd.org; dvbid at cdc.gov; nck6 at cdc.gov;
> pbright at abcbirds.org; esaito at usgs.gov; marrap at si.edu;
> savetheocean at yahoo.com; JacobsburgEEProgramssp at state.pa.us;
> Jimsmith0212 at aol.com; harrypav at hotmail.com; twalker at ifas.ufl.edu
> Subject:	[leps-talk] Non-avian vectors and rapid spread of WNV
> 
> Bob Augustine (see below) provided an innovative suggestion of how a
> non-avian vector (particularly Pieris rapae) might account for the
> spread of WNV.
> I think it is important to think creatively about West Nile ecology and
> to recognize that the most interesting aspects lie outside of humans. 
> 
> I have believed that the gap in our knowledge of "rapid spread" may
> represent a lag between the time the virus arrives and begins to
> multiply in local avian reservoirs, and the time it is "discovered" due
> to either avian, equine, or human morbidity or mortality. 
> 
> Thus the rapid spread may be in artifact of our sampling and monitoring
> programs.  
> 
> As author of a book on Butterflies of New Jersey, and as an observer on
> the current Cabbage Butterfly population explosion (late July 2003) in
> central NJ, I have more than a passing interest in the Augustine
> proposal. I will also circulate it to the two lepidoptera list servers I
> subscribe to and see if there are other perspectives. 
> 
> I am grateful to Bob for pointing out the Walker paper on butterfly
> migration at Gainesville, FL.  It points to a net northward movement of
> Cabbage Butterflies in spring AT THAT SITE.   In New Jersey we do not
> think of Cabbage White's as particularly migratory (either north or
> south), BUT I WILL ASK THE LIST MEMBERS WHAT HAPPENS AT OTHER
> LOCALITIES.  
> 
> Also quite a few butterflies feed on bird droppings, BUT I CAN'T RECALL
> SEEING A CABBAGE WHITE AT BIRD DROPPINGS.  PERHAPS OTHER LIST MEMBERS
> HAVE A DIFFERENT EXPERIENCE. 
> 
> Most of the other migratory butterflies irrupt from the southwest or
> south into the northeast, which doesn't seem the right direction.  The
> Monarch, of course, has dramatic southward and westward migrations in
> Sept-Oct, which would be the right time to carry a virus from the index
> cases in the northeast----but I don't recall ever seeing a Monarch at
> bird droppings.  I'll post that question also. 
> 
> Dragonflies, now there's a thought.  Lots of good southward migrant
> species and mosquito eaters. 
> 
> Michael Gochfeld
> 
> 
> 
> 
> Bob Augustine wrote:
> > 
> > A proposed new WNV vector (and other WNV observations)
> > 
> > In a previous (unanswered) e-mail I suggested that we need to find
> another vector that travels en-
> > masse, south to north, in June or July to explain 2002's rapid extension
> of WNV concentration
> > from the Gulf coast to the upper Midwest. Since bird movements do not
> match this pattern, I
> > further suggested that dragonflies, butterflies, or moths might.
> > 
> > Only a few butterfly species are known to migrate at all, but more are
> coming to light. In recent
> > correspondence, an article published in 2001* revealed that the
> (imported) Cabbage White, Pieris
> > rapae, (said by some to now be the most abundant butterfly in North
> America) sometimes has a
> > very marked late spring eruption northward. Recent postings on Internet
> listservs from PA and NJ
> > report unusually high numbers of this species this year. Its association
> with cabbage-also a food
> > plant of the Fall Army Worm, Spodoptera frugiperda, noted as having
> invaded Ontario from MS
> > in September 1973-and this migratory pattern (most evident in the record
> from 1987) lead me to
> > propose the Cabbage White as a potential WNV vector. I don't think
> mosquitoes bite butterflies
> > or caterpillars, however, these butterflies are known to extract
> minerals from bird droppings,
> > which may be the way they pick up the virus (if they do).
> > 
> > I urge the CDC to investigate the Cabbage White as a possible West Nile
> Virus vector, as well as
> > other insect pests of cruciferous plants with northward summer
> movements.
> > 
> > Another dot to connect in this mystery just surfaced in a posting from
> NJ. As you may know,
> > catnip has been found to be 10 times as effective as a mosquito
> repellent as DEET. Catnip is not
> > only among the plants Cabbage Whites are reported to be feeding on in
> NJ, the poster
> > writes,"First thing in the morning the cabbages congregate on catnip,
> even in the shade."
> > 
> > I also wrote earlier that the CDC maps for 2002 offered no clues as to
> geographical routes of
> > transmission. In the 2003 bird map, however, there is a marked tendency
> for positives to cluster
> > along river valleys. This may simply be because humans concentrate in
> such areas and are thus
> > more likely to find dead birds there. On the other hand, I think the
> pattern is a bit too extensive to
> > be explained this way. If there is a corridor effect, I reiterate that
> bird numbers (post-breeding
> > wanderers-egrets, herons etc.) are too few to support a bird vector
> hypothesis. But butterflies
> > that migrate north in summer in larger numbers are also noted for taking
> river valley routes in
> > doing so. If moths behave in a similar fashion, they could also account
> for this pattern, flying
> > undetected at night.
> > 
> > It is interesting to observe that so far in 2003 the largest number of
> human WNV cases (36) is in
> > CO, not IL, LA,MS or the other places that were focal points of the last
> 2 years. It almost
> > appears that the disease is waning in those areas now. Perhaps immunity
> develops in humans in
> > only a couple of years as it seems to have in birds in the East (and
> perhaps in Europe). This would
> > be really good news.
> > 
> > The spread pattern on the bird map would be easier to see if more
> counties did testing. This year
> > it seems fewer have along the corridors than last year. The white
> (untested) areas have to be
> > ignored and only the green (tested) regions provide a useful context for
> the positive test results.
> > 
> > *Butterfly Migrations in Florida: Seasonal Patterns and Long-Term
> Changes, Thomas J. Walker,
> > U. Fla., Gainesville, Environ. Entomol. 30(6): 1052-1060 (2001)
> > http://esa.edoc.com/environ/v30n6/v30n6p1052.pdf
> > 
> > Bob Augustine
> > raugustine at tms-hq.com
> > Rockville, MD
> 
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