Avian Influenza (AI)- Risk assessment and management
The fear from the penetrating of AI type H5N1 exists all over the world. In order to
avoid completely the possibility of the disease from penetrating, one has to build a
diagnosing survey system for birds that appears to be extremely expensive. One has
also to be prepared for a massive bird destruction, which would be employed in
case the surveys results would be positive.
One could assume with high probability, that it would be impossible to avoid an
epidemic outbreak in avian industry because:
1. The investment in prevention measures in the avian industry is insufficient.
2. The investment in preventing the first outbreak is insufficient.
In the analyzing the steps and policy to be taken against the penetration of AI in the
avian industry one must take in account the damage of considering the risk,
probability, cost in minimizing the risk of the disease entering the country. If in a
possible policy, the costs of the items would be too large and the risk would be
small, it is obvious that not steps would be taken prior to the first outbreak.
Action categories combination in decision-making
Probably
Risk
for a risk
costs
High
Low
High
Low
High
High
Low
High
Low
Low
Costs in
lowering
the risk
To take
Action?
Low
High
High
Low
High
Yes
No
Yes
Yes
No
The risk probability estimate is based on quantity and epidemiological data.
The risk damage is based on economic data. Combination of all those
categories could enable the policy makers to decide whether to accept or
reject a policy. In the above table the emphasized policies would certainly be
rejected.
Tests were conducted on farms keeping game or back yard fowls near a lake,
as it was believed according to world publications, that wild water birds are
the main carriers and vectors of AI H5N1
Percentage of wild water birds found near fowl farms situated by a lake
Game birds
16%(1.6SE)
Back yard birds
38.4%(3.6SE)
One could assume that wild water birds are indeed attracted to farms situated
near lakes and could infect farm fowls which are free on the ranch and are
unprotected in hen-houses.
It is hard to estimate the spread magnitude and the damage in affected farm
birds when an outbreak would occur. Therefore estimations are based on
experts understanding and are divided into “low” or “high” etc. This
approach is inaccurate, but is feasible and not so far from reality. Those
terms as “low” or “high” are relative concepts and not definite.
A diagram describing a possibility of AI N1H5 entering Israel
Zoo anim als
W ild birds
M igrating birds
Im port
Back yard
birds
Pet birds
O rganic poultry
Farm poultry
Foreign w orkers
Analyzing possible risks
Risk 1
The possibility of importing contaminated farm poultry or pet birds that will
infect local poultries:
Farm
Commercial
Personnel
Smuggled
poultry
pet birds
import
pet birds
import
pet birds
Very low
Very low
Low
Risk 2
Bringing the infection by foreign workers. The Americans have estimated
that the risk for HPAI from Mexico to the USA should be categorized as
high. It is well known that in Israel many foreign workers, which work in the
poultry industry, originate from Thailand in which AI H5N1 exists. Those
incoming workers might bring with them HPAI H5N1 on their shoes or
clothes. The virus might enter the country within 48 hours after leaving a
small village in Thailand due to the fast air transport. The conclusion
therefore that this way is of high risk. To minimize this risk it is advised to
control more intensively the incoming workers from the Far East with direct
or indirect flights.
It is strongly advised the farmers to demand that all workers will wash
themselves, wear only clean clothes and shoes when entering the poultry
Medium
farms or hen-house. It would be wise not to occupy a foreign worker
immediately at his arrival, but wait a while to assure that he does not harbor
any risk.
Risk 3
It is possible that the virus might penetrate by migrating wild birds. Much is not
known of this kind of risk. Wild water migrating birds could harbor and be carriers
of the virus. “Twice every year almost 500 million fly-pass Israel in which some
are water wild birds”. Some of them stay for the winter in Israel. It is proposed that
part of them is infected with the virus.
The conclusion is that the risk is high.
OIE declared that no country could declare free of HPAI in wild birds.
Let us assume that 10,000 migrating birds are infected. To find only one infected
birds out of a 500 million birds with 95% certainty and a specifity of 100% one
must test 15,000 birds!!! Finding one such an infected bird will not help because
there are sill 9,999 infected wild birds flying over the country. Even if we know
that wild migrating water birds harbor the disease there is no practical act to be
taken against the disease.
Cost/ benefit of monitoring birds for the virus:
The monitoring costs are extremely high, with very little benefit. Finding a positive
result would stop all export of reproduction material, fresh meat, and harm tourism.
Finding one such a positive case in a wild bird would enforce quarantine on the
area and destroy all the farm poultry in that area. That action is not practical, and it
would be better to adopt biology security measures. Those measures include the
veterinarians, farmers, slaughterhouses, food industry and back-yard poultry
farmers.
International monitoring migrating birds will be of some value if:
1. A positive finding would not influence the countries disease status.
2. Agreement upon the goal of such research.
3. Finding the sample size that will give some impact.
4. Agreement upon avian species to be tested.
5. Agreement upon season and place to be tested.
6. The way the captured birds should be marked.
7. Uniformity in the test to be applied.
8. Uniformity in analyzing the results.
Such a vast investigation could be done only with international and neighbor
countries collaboration.
Risk 4
Infecting “organic” poultry, back yard, pet poultry and zoos from migrating birds.
In most cases back yard poultry were the first infected. The first case occurred in
Holland in “free egg layers chickens”. All those kind of poultry are not isolated
from migrating birds and the contact with them is unavoidable. Most of the
holdings in Israel of back yard poultry are not authorized. E. Berman/ M. VanHam