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FOOT-AND-MOUTH DISEASE VIRUS, HUMAN CARRIAGE

A ProMED-mail post
http://www.promedmail.org>
ProMED-mail, a program of the
International Society for Infectious Diseases
http://www.isid.org>

[see also:
Foot-and-mouth disease virus, human carriage 20010403.0667]

Date: 4 Apr 2001
From: Paul Goldwater <

Notwithstanding the Pirbright experiments (1), it would be almost certain
that with the tool of RT-PCR we would be able to demonstrate FMDV in nasal swabs of anybody who was in the vicinity of an infected animal.

The apparent transmission by man simply carrying virus in his nose may be
important, but more important would be the truly infected human who would
probably shed far more virus than the passive uninfected brief "nasal
carrier." We must remember that FMDV can infect humans either
symptomatically or asymptomatically (2). Therefore infected humans
(shedding virus) would likely play a more important role in virus
transmission than the brief nasal carrier. Human infection seems to have
been overlooked by the UK epizootic managers.

Veterinary officers (and others) involved in inspecting livestock and who
become infected could be responsible for the epizootic's unrelenting
spread. I am surprised that the use of zinc compounds (3,4) (which are
plentiful and cheap) for prevention and treatment of infection has not been
explored as a means of limiting the current epizootic in the UK.

References:

1. Sellers RF, Herniman KAJ and Mann JA (1971). Transfer of foot-and-mouth disease virus in the nose of man from infected to non-infected animals.Veterinary Record, 89, 447-449.

2. Bauer K. Foot- and-mouth disease as zoonosis. Arch Virol Suppl
1997;13:95-7.

3. Firpo EJ, Palma EL. Inhibition of foot and mouth disease virus and
procapsid synthesis by zinc ions. Arch Virol. 1979; 61:175-81.

4. Polatnick J, Bachrach HL. Effect of zinc and other chemical agents on
foot-and-mouth-disease virus replication. Antimicrob Agents Chemother.
1978;13: 731-4

- --
Dr Paul N. Goldwater, FRACP, FRCPA,
Medical Head, Virology, & Senior Consultant Clinical
Microbiologist/Physician in Infectious Diseases,
Microbiology & Infectious Diseases Department,
The Women's & Children's Hospital,
North Adelaide, South Australia 5006.
<

******
[2]
Date: 4 Apr 2001
From: Howard Pharo <>


It would indeed be interesting to see trials being done using PCR to assess the prevalence and duration of nasal carriage in humans who were in the vicinity of an infected animal. I would imagine there might be some
difficulties in defining "in the vicinity of" in this case -- would it mean
on the same property, in the same barn, or within a specified distance (of
what particular animal orifice?). Even more interesting would be to see
further attempts to assess the relevance of nasal carriage in terms of the
potential to infect animals.

In the meantime, we have to rely on speculation based on the work of
Sellers and others from the 1970s, which simply indicates it "is possible."
 From a risk assessment point of view that is not particularly helpful.

For instance, we in New Zealand have sent teams of veterinarians to assist
UK MAFF in controlling this FMD outbreak. The question arises how long must we consider our returning veterinarians to be potentially a risk, and from this comes the concept of the stand-down period, which we currently set at 7 days (the USDA set their stand-down at 5 days, based on the same information as we have). The stand-down period also applies in the case of persons involved with diagnosis or animal disposal on infected properties
in the UK.

Concerning the "truly infected human carrier" who would "probably" shed far more virus than passive nasal carriers, I am not really able to comment.
However, it is my understanding that there have only been 37 human cases of FMD recorded in the literature (Donaldson & Knowles, 2001) and that there is quite frequent confusion on this point between the ungulate disease FMD (caused by an apthovirus) and the human disease "hand, foot and mouth disease" (caused by enterovirus 71).

It is not clear what Dr Goldwater is suggesting should be done with the
zinc compounds in respect to limiting the current epizootic in the UK.

Reference:

Donaldson A, Knowles. Foot and mouth disease in man. Veterinary Record, Vol
148 (No 10), p 319, March
 
­­
Howard J Pharo
National Adviser, Risk Analysis
Animal Biosecurity
MAF Biosecurity Authority
ASB Bank House
Wellington, New Zealand
<>

[Interesting exchange. I think Dr. Pharo's point is well taken; the
confusion between hand, foot and mouth disease is quite common. Thank you both. - Mod.TG]

------------------------------

End of ProMED Digest V2001 #79


A ProMED-mail post
http://www.promedmail.org>
ProMED-mail, a program of the
International Society for Infectious Diseases
http://www.isid.org>

[see also:
Foot & mouth disease - EU: use of vaccination (03) 20010329.0636]

Date: 3 Apr 2001
From: Jack Woodall <>

Mass culling? Not for the USA
- --------------------------------------
A previous post on ProMED-mail (reference above) discussed why vaccination
is out of the question for controlling a future FMD outbreak in the USA; it
could be used for protecting breeding stock. This contribution discusses
why mass culling -- as opposed to selective culling -- although being used
in the UK, is also out of the question for the USA.

There are several arguments against mass culling, which taken together add
up to making it an impossible task for a country with the density of
livestock the USA has in many states. First, it kills many adult animals
which would otherwise have survived infection, albeit with perhaps a 10
percent loss in productivity (as compared with a 100 percent loss if they
were killed). That leaves a legacy of surviving but infectious animals,
which would take perhaps years to eliminate in order for the USA to return
to FMD-free status.

But since Japan & South Korea, which together account for over 60 percent
of US beef & pork exports, will ban imports of both from the US at the
first report of an outbreak (Australia and New Zealand will be only too
glad to fill the gap), a 10 percent loss in meat production would not
affect the capacity to export to other markets.

Second, the logistics of slaughtering and disposal of possibly millions of
head of livestock quickly overwhelms capacity. During the FMD outbreak in
Taiwan in 1997, 4 million pigs were culled, at a peak rate of 130 000 per
day, after the army got up to speed. Let´s say the US Army could do the
same on the larger US feed lots. That´s still 30 days to kill 4 million; 30
days in which the disease is still spreading. It is questionable, however,
whether the public would stand for the TV spectacle of the US Army or
National Guard shooting livestock. Even the UK has not yet gone that far.

Third, the risk of delays due to litigation are great. Farmers and national
associations of breeders would seek injunctions, animal rights and
environmental groups would do the same. Slaughtering could be held up for
weeks. Also, the huge amounts of money needed to finance a big emergency
would exceed existing provisions and require additional legislation,
preceded by much debate, before being approved. Even emergency funds from
the White House would take time to arrive. My experience with public health
authorities has shown that they will always live in hope that the outbreak
will be contained with minimum expenditure, leading inevitably to too
little funding too late to do any good. I have no reason to believe animal
health authorities will react differently.

Models exist that purport to show for US conditions under the most
optimistic circumstances, if culling of 95 percent of latently infected
plus infectious herds can be achieved beginning in the second week after
recognition of the first outbreak, "only" 20 percent of an affected
region´s herds need be destroyed to achieve control. But if culling to that
level is delayed by just one week, the eventual destruction will have to be
more than 90 percent. I don´t think anyone can seriously believe any state
agency is going to be able to move that fast, or be able to cull to that level.

Finally, a recent analysis of the potential cost of FMD in California
projects direct costs, plus production losses, plus trade losses would sum
to around US$8000 per head culled, or US$ 8 billion per million head -- and
this may be a conservative estimate. Twenty percent of the cattle in Texas
alone is 1.6 million head.

I rest my case.

References:

Ekboir J 1999. Potential impact of Foot and Mouth Disease in California.
Agricultural Issues Center, Div Ag & Nat Res, Univ. Cal. Davis.

Woodall J 2001. Vaccination? Not for the USA. In Foot & mouth disease - EU:
use of vaccination (03), ProMED-mail archive no. 20010329.0636 29 Mar
http://www.promedmail.org/pls/promed/promed.searchhtml.showmail?p_filename=20010329.0636&p_year=2001&p_month=03

Yang PC, Chu RM, Chung WB, Sung HT 1999. Epidemiological characteristics
and financial costs of the 1997 Foot and Mouth Disease epidemic in Taiwan.
Vet Rec 145 (25): 731-734.

­­
Jack Woodall
Nucleus for Investigating Emerging Infectious Diseases
Dept. of Medical Biochemistry
Institute of Biomedical Sciences
Federal University of Rio de Janeiro
Rio de Janeiro, Brazil
<>