BOOKS OF RtfiDIfGS - PAHO/WHO

- 94 -
RABILES CONTIROL IN tURIAN COLOMBIA
IMMIGRATING RABID DOGS
ISNS SUS g
sus sus RABID
SU SUS SUS SUS--WLDLIFE
SWILDLIFE
sUS
RABID . 'SUS S U s SUS
WILDLIFE T
4SUSSUS S US
IMMIGRATING RABID DOGS
FIoURE 2. Movement of inective rabid dogs and wildlife into and through a spatial grid representing
an urban area. Abbrev.: INF - infeclive rabid dog. SUS - susceptible dog. g - probability of movemenl in a
given direction.
barrio and possibly, depending on the amount of contact, continues the transmission
of the disease.
A certain number, W, of rabid wildlife (see Figures I and 2) enter the peripheral
barrios of the city and interact with the susceptible dog population. The wildlife are
given the opportunity to make only one move since it appears likely that a wild
antimal would be killed before it could roam very far in a city. Once in tihe urban area,
the rabid wild animals are included in the infective state, Y.
Urban canine population growth, G, in every barrio (see Figure 1) is assumed to be
proportional to the human population growth in that barrio [37]. The assumption is
also made that these entering dogs are not vaccinated and therefore increase the
susceptible canine population in a specified barrio by G. per day. Some of the newly
arriving dogs may have had contact with rabies outside the system and be currently
incubating the disease. A certain number, M, would become part of the infective state,
Y, during the year (see Figures I and 2). The probability that they will appear in any
specific barrio is dependent on the proportion of the city's human population
presently living in that barrio. The assumption is based on the idea that the more
people there are in an area, the greater is the chance that their dogs will have had
some interaction with other dogs in surrounding areas or cities where rabies currently
exists.
The model accepts as inputs the vaccination schedule. the number of vaccinating
teamnis and trucks, and tlhe numher of rabid dogs anid rabid wildlife which enter ealch
year fromi outside tihe system.
3. Exsperiteicnts Usinsg itLe Model
Since ti,e model is stochastic. numerous epidemic trails were run per experiment in
order to determine thc mican numbcl cunmulative rabid dogs atl he end of o íevery
year. All costs mentioned in the following sections are estimates. based on Colombian