Rev. sci. tech. Off. int. Epiz.,
1989, 8 (3), 733-745.
Population density and ecology of dogs
in Nigeria: a pilot study
S.I. OBOEGBULEM * and I.E. NWAKONOBI **
Summary: The population dynamics of dogs is an important factor in the
epidemiology of endemic canine rabies. Lack of reliable estimates of dog
populations hampers rabies control campaigns in developing countries, as costbenefit analysis of control strategies cannot be made accurately. The WHO
"Guidelines for dog rabies control" has stressed the need for research on dog
populations and ecology in urban and rural areas. Determination of dog
population density (dogs/km ) from established indicators of dog abundance
(dog to human ratio and dogs per household) is one recommended procedure.
2
Using a questionnaire, we carried out a pilot study in selected urban and
rural areas of Nigeria, in order to establish the population density and structure
of owned dogs, differences in frequency distribution and population densities
of dogs in households in urban and rural areas, and factors which promote
straying of owned dogs.
More dogs were owned by urban households than in the rural areas. The
association between the number of dog-owning households and locality (urban
or rural) was highly significant. There was also a significant association between
the number of dogs in a household and locality. The dog to man ratios for urban
and rural areas were also calculated. By both indicators, the abundance of dogs
in the urban area was twice that of the rural areas. Calculated from the dog
to human ratios and projected human population densities, the population
density of owned dogs in the urban (131/km ) was 8.8 times that in the rural
areas (15/km ). The male:female ratios and age distribution of dogs for urban
and rural areas were also calculated.
2
2
The epidemiological and public health implications of large urban dog
populations, partial confinement and free range of owned dogs in urban and
rural communities include promotion of straying, gathering of dogs in packs,
easy contact with strays and wildlife, and increased risk of human exposure
to dog bites and to rabies.
The survey method employed in this pilot study is economically
logistically feasible in most developing countries.
and
KEYWORDS: Dogs - Nigeria - Population statistics - Rabies.
* Present address: Department of Community Medicine, University of Glasgow, Glasgow G12 8QQ,
United Kingdom.
** Department of Veterinary Pathology and Microbiology, Univerity of Nigeria, Nsukka, Nigeria.
734
INTRODUCTION
Dogs are kept by most African peoples. The reasons for keeping dogs, their value
and veterinary care tend to vary according to the culture, status, social interests and
economic activities of the people. In b o t h u r b a n and rural areas there are a b u n d a n t ,
t h o u g h largely undefined populations of owned and stray dogs. In Nigeria, the dog
population has been variously estimated at between 3 and 5 million, but the estimates
are not based on established parameters. The W H O "Guidelines for dog rabies
c o n t r o l " (23) stresses the need for research o n the population and ecology of dogs
in urban and rural areas. Published studies have been carried out in the U S A (10,
15, 17, 18, 21), J a p a n (5), Philippines (3), Mexico (20), etc. A p a r t from the review
by F r a n k (11), there appears to be no published study on the population and ecology
of dogs in Africa. Such a study is particularly relevant in Africa where the dog is
the primary vector of rabies (6, 23). Population dynamics and ecology of the principal
animal reservoir influence the epidemiology and control of rabies. Lack of accurate
estimates of dog populations is a fundamental handicap in rabies control programmes.
Cost-benefit analysis of control strategies (such as mass vaccination) cannot be
m a d e without reliable information o n the population distribution of dogs and
accessibility of dogs to vaccination campaigns (23). Bögel and Motschwiller (4)
observed that careful analysis of the number of dogs accessible to vaccination is
required to assess the cost-effectiveness of eliminating rabies from its canine reservoir.
Unlike livestock kept in herds on farms or housed in flocks, dogs are owned in
small numbers in widely and randomly scattered households. There appears to be
n o standardised field technique available for general application in dog population
studies. One parameter is an estimation of dog population density, calculated from
the dog to m a n ratio or dog per household and expressed as dog per unit area (23).
Various workers have applied different techniques for estimating dog population
densities. These techniques include total street-dog count (23), estimates from the
rate of capture (7) and estimates from rate of re-capture of the same dog (2). Most
of these methods are adapted from techniques developed for estimating the density
of wild animals in their natural habitat (23). For sylvatic rabies to become endemic
in a given geographical area of E u r o p e , the local fox population density needs to
be at least 0.25-1.0 f o x / k m ( 1 , 19, 22). Such a transmission threshold also ensures
the endemicity of canine rabies, and it needs to be determined for developing countries.
Establishing an acceptable parameter for dog population density is a necessary first
step.
2
The number of owned dogs may be established from records kept for dog licensing
(16, 20, 21). However, in Africa, where a high proportion of owned dogs are not
licensed, data on the owned dog population and ecology can be obtained by crosssectional studies, based on a questionnaire survey. Using this methodology,
recommended by the W H O (23), we carried out a pilot study on the population density
a n d some aspects of ecology of owned dogs in selected urban and rural areas in
Nigeria. The specific aims of the study were as follows:
- W h a t is the dog population density (estimated from dogs per household and
dog to m a n ratio) in the areas of study? Is there any association between locality
and frequency distribution of owned dogs? Is there a significant difference in
population densities of owned dogs in urban and rural areas?
735
- W h a t is the population structure (age distribution, sex ratio, breeds) of dogs
in u r b a n and rural areas?
- W h a t are the major reasons for keeping dogs and what factors p r o m o t e the
straying of owned dogs (e.g. feeding habits, degree of confinement, socio-cultural
patterns of the community)?
- W h a t proportion of dog-owning households have licensed dogs and rabies
vaccination certificates?
MATERIALS A N D METHODS
Sample survey design
For estimating dog population density in relation t o household, W H O (23)
recommends sampling 500 t o 5,000 households in a major survey. In our pilot study,
the survey was designed to sample 500 households in the metropolis and in each rural
town selected. The h u m a n population in Nigeria is about 2 5 % urban and 7 5 % rural.
Therefore, one u r b a n area and three rural areas were surveyed, in proportion to the
h u m a n population distribution. For the urban area, Lagos mainland was chosen. F o r
the rural areas, Utchi (in N d o k w a Local Government Area (LGA), Bendel State),
A w o - O m a m m a (ORU L G A , I m o State) and Obollo (Isi-Uzo L G A , A n a m b r a State)
were surveyed.
A modification of the design of the United Kingdom General Household Survey
(13) was adopted. In Lagos mainland, a simple r a n d o m sample of the metropolitan
zones was made, and Festac and Sumiere were selected. A stratified r a n d o m sampling
of the streets/roads in these zones was carried out, followed by further stratified
sampling of households (house numbers) in the respective streets and roads selected.
In Utchi, where proportions of the population live in quarters (main villages) and
in camps in the farming areas, four quarters and four camps (farmsteads) were
selected. In the other rural towns of Obollo and A w o , a stratified r a n d o m sampling
of wards in each t o w n was m a d e . Households in each selected q u a r t e r / c a m p or ward
were visited until 500 households had been surveyed for each rural area.
Survey method
A questionnaire was issued to the head or senior member of each household. Where
n o member of a household was sufficiently literate, the questions were read out and
explained to the respondent, and the answers given were filled in by the interviewer.
P a r t A of the questionnaire solicited information on the n u m b e r of persons in
the household, whether or not the household owns any dogs, the number of dogs,
reasons for keeping them, etc. P a r t B sought specific information on individual dogs:
breed, sex, age; whether each dog has been licensed and evidence of a valid licence;
rabies vaccination history; t o t a l / p a r t i a l confinement or free movement of the dog;
feeding habits (whether the dog is fed by the owners and neighbours or selfscavenging).
736
RESULTS
Dog population density/frequency distribution
Urban versus rural
Dogs were owned by 191 of 500 households (38.2%) sampled in Lagos mainland.
T h e total number of dogs in the area was 250, giving a dog:househoId ratio of 50:100
(Table I). F o r the three rural towns combined, 306 of the 1,500 households (20.4%)
owned dogs, a ratio of 26:100 households. This suggests that owned dogs were twice
as a b u n d a n t in u r b a n as in rural areas. There was a highly significant association
between locality (urban versus rural) and the number of households with dogs
( X = 64, Table IV). There was also an association between the number of dogs in
a household ( 0 , 1 , > 1) and locality (X = 63.5, Table IV). The frequency distribution
of dogs in households was significantly higher in the u r b a n t h a n in the rural areas
(t = 4.18, p < 0.01, Table V).
2
2
T h e dog to m a n ratios for u r b a n and rural areas were 1:21 and 1:45 or 47 per
1,000 persons and 21.7 per 1,000 persons, respectively (Table II). This again indicates
that the abundance of owned dogs in the u r b a n area is twice that of the rural areas.
On the basis of d o g / h u m a n ratios and the projected h u m a n population densities
of 2 , 7 6 2 / k m and 6 9 1 / k m for u r b a n and rural areas, respectively (Table II), the
2
2
TABLE I
Dog population
distribution in sampled
rural areas in Nigeria
urban
and
H o u s e h o l d s with number of
dogs
Areas
surveyed
I. Urban
(Lagos)
A. Festac
B. Sumiere
II. Rural
A. Utchi
(Bendel State)
1. Main village
2. Farmsteads
(camps)
B. Awo-Omamma
(Imo State)
C. Obollo
(Anambra State)
III. Urban and rural
combined
House­
holds
surveyed
Total Dogs/100
dogs
house­
holds
0
1
2
> 2
Total
households
owning dogs
500
250
250
250
143
107
50
57
43
309
140
169
141
81
60
41
25
16
9
4
5
191
110
81
(38.2%)
(44.0%)
(32.4%)
1,500
391
26
1,194
237
53
16
306
(20.4%)
500
400
89
9
18
4
433
391
48
9
16
0
3
0
67
9
(13.4%)
(2.3%)
100
80
80
42
39
16
3
58
(58%)
500
116
23
409
72
13
6
91
(18.2%)
500
186
37
352
117
24
7
143
(29.6%)
2,000
649
33
1,503
378
94
25
499
(24.9%)
737
T A B L E II
Dog to man ratio and dog population
in urban and rural areas
Urban
Surulere
Festac
No. of house­
holds sampled
Average number
of persons per
household
Total number
of persons
Total number
of dogs
Dogs/1,000
persons
Dog to man ratio
Projected human
population
density/km
Dog population
density/km
250
250
9.8
11.3
density
Total
Utchi
Rural
Awo
Obollo
500
500
500
10.5
11.5
13.4
500
12.1
Total
1,500
12.0
2,450
2,825
5,275
5,249
6,702
6,051
18,002
143
107
250
89
116
186
391
58.4
1:17
37.9
1:26
47.4
1:21
17
1:59
16
1:62
30
1:33
21.7
1:45
2
2,506
3,018
2,762
676
1,037
361
691
2
146
114
131
11
17
11
15
2
2
dog population densities are 1 3 1 / k m and 1 5 / k m for the u r b a n and rural areas. This
means that for the areas surveyed, the population density of owned dogs in the urban
area is 8.8 times t h a t in the rural areas.
Within urban
areas
A m o n g the 250 households sampled in Festac and in Surulere (Lagos metropolis),
there were 143 and 107 owned dogs, equivalent to population ratios of 57/100 and
43/100 households, respectively (Table I). For the two metropolitan zones the
proportions of households that owned dogs were 4 4 % and 3 2 . 4 % . The frequency
distribution of dogs was significantly higher in Festac t h a n in Surulere, b o t h by the
t-test (t = 2.34, p < 0.05, Table V) and by the 9 5 % confidence interval estimate
(0.14 to 0.16).
The dog to m a n ratios for Festac and Surulere were 1:17 and 1:26, or 58 per 1,000
and 38 per 1,000 persons, respectively; and the population densities of owned dogs
were 1 4 6 / k m and 1 1 4 / k m (Table II).
2
Within rural
2
areas
For the three rural towns (Utchi, A w o and Obollo) the dog population ratios were
18, 23 and 37 per 100 households (Table I). As within the u r b a n area, the n u m b e r
of dog-owning households was related to location of the various rural communities.
However, by the t-test analysis, the difference in frequency distribution of dogs in
the households, between two rural towns (Awo and Obollo) was not statistically
#
O oo
O O <N
CN ^j- m
oo r^t <
-3- ~*
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r- oo (N
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h
O
MD
^
m
MD
o m
O
co O
m r- ^-^
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o
(49%)
1 1 1 (94%)
175 (94%)
5 (4%)
11 (6%)
0 (0)
0 (0)
91
186
ë~~
i—«
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ON
oo r— C N
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i -^t -—i
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oo
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37%
oo
M (N
12%
fS)
"y~i
CO
2%
MD
co
-Tt
24%
Rural
Obollo
CO
11%
(45%)
0.96:1
OO
ON
Total
175 (43%)
0.8:1
300
11
80
(76.7%)
(2.8%)
(20.5%)
21.7%
M D ci >—i ••—i
—« r-i T J - — <
34%
O O O ^-i
^ CI
-
194 (77.6%) 89 (100%)
56 (22.4%)
0 (0)
0 (0)
0 (0)
52
116
^
^ i
Un
Proportion of dogs
validly vaccinated
against rabies
OO
^
^ ^ # #
o~ i—i M D O O
m m
O
Pet
Guard
Hunting
Other
cN —<
u-t m ^
#
m
^ íe
MD
y—s
MD
Function of dogs
89
Awo
119 (48%) 32 (36%)
0.9:1 0.56:1 0.8:1
i#
oo
c*l
Never
Partial (d/n)
Always
(46%)
0.85:1
250
Utchi
m
v-t
OO
Confinement
49
107
Total
# # #
Oí cs
S- S o
r—
QO 45 ^~
Native (mongrel)
Exotic
Mixed
Urban
Surulere
t
oo
Breed
< 1 year
1-5 years
> 5 years
Age
70 (49%)
0.96:1
143
Festac
S\
m
Male
Male:female ratio
Sex
Number of dogs
Parameters
Dog population structure in urban and rural areas
TABLE III
738
^ # # #
&- ^J- m ^-t
rN M
n
IT)
(N
MD
O
w~) OA O
o
•—< m O 0\
OO
i—t
739
TABLE IV
Chi-square
analysis of dog population
Households
Urban
versus
rural areas
Urban
Rural
Total
With dogs
191
(124)
306
(393)
497
Without dogs
309
(376)
1,194
(1,127)
1,503
500
1,500
2,000
Festac
Surulere
Total
110
(95.5)
81
(95.5)
191
140
(154.5)
169
(154.5)
309
250
250
500
With dogs
Within
rural
areas
2
X
2
7.2
Without dogs
Households
Utchi
Awo
Obollo
Total
With dogs
67
(102)
91
(102)
148
(102)
306
Without dogs
433
(398)
409
(398)
352
(398)
1,194
500
500
500
1,500
2
X
64.6
Number of dogs
in a household
Urban
0
Urban
versus
rural
X
64
Households
Within
urban
area
distribution
1
> 1
Number of households
Rural
Total
309
(376)
141
(95)
50
(30)
1,194
(1,127)
237
(237)
69
(89)
1,503
500
1,500
2,000
378
X
2
63.5
119
significant (t = 1.65, p < 0.05). T h e proportions of dog-owning households in the
two towns were 18.2% and 2 9 . 6 % . In Utchi the distribution of dogs in households
was rather skewed. While only 9 of 400 households (2.3%) in the quarters (mainland
villages) owned dogs, as m a n y as 58 of 100 households in the camps (farmsteads)
owned dogs (Table I).
On the basis of dog to m a n ratio, the population densities in the three rural towns
were 11, 17, and 11 per k m (Table II).
2
740
TABLE V
Frequency
Area
(locality)
distribution
of dogs in households
Number
of households
sampled
(n)
Urban
Number of
dog-owning
households
in urban and rural
Mean of
dogs per
household
(x)
Standard
deviations of
dog frequency
(S )
191
1..36
19.49
1 ,500
306
- 0 . .31
52.83
Within urban areas:
Festac
250
110
0..58
0.74
0..43
0.70
7
7
0..23
0.55
0.,36
0.63
Surulere
250
81
Within rural areas:
Utchi
Awo
500
500
67*
91
Obollo
500
143
t-test
(t)
2
500
Rural
areas
Urban vs.
rural:
4.18
(p < 0.01)
Festac vs.
Surulere
2.34
(p < 0.05)
Awo vs.
Obollo
1.65
(P < 0.05)
* Distribution in Utchi was skewed. Only 9 out of 400 households in the quarters (mainland village), and
58 out of 100 households in the camps (farmsteads).
Population structure of dogs
Table III summarises the population structure of dogs in both urban and rural
areas. Of the 250 dogs in households sampled in Lagos metropolis, 48°7o were male.
For the rural areas combined, 4 3 % of 391 dogs were male. The male:female ratio
was 0.9:1 for u r b a n and 0.8:1 for rural areas. There was no significant difference
in sex distribution of dogs in urban and rural areas. Dogs less than a year old accounted
for 5 7 % of the u r b a n and 4 6 % of the rural population; 3 2 % and 4 2 % were 1-5 years
old, while 1 1 % and 12% were more than 5 years old. The difference in age distribution
in u r b a n and rural areas was statistically significant (X = 7.26). Eighty-four of the
250 dogs in Lagos (34%) and 300 of 391 dogs in rural areas (76.7%) were of the
native, mongrel breed. A total of 122 dogs in u r b a n (49%) and 11 in the rural areas
(2.8%) were exotic breeds. The major exotic breeds in Lagos were Alsatian (German
Shepherd), 8 0 % ; Dachshund, 1 0 % ; terrier, 5 % ; and D o b e r m a n , 2 % .
2
At the time of the survey, 2 4 % of the dogs in Lagos u r b a n and 2 1 . 7 % in the
rural areas were validly vaccinated against rabies. Some households claimed that their
dogs had been vaccinated " o n c e " - two or more years ago! Since annual revaccination is recommended for rabies vaccines available in Nigeria, such vaccination
certificates could not be considered valid.
On the function of dogs or the reasons for keeping them, 3 0 % of owned dogs
in the urban area but only 4 % in the rural areas were kept as pets; 4 5 % of dogs in
the u r b a n and 31 % in the rural areas were kept as guards. While n o u r b a n dog was
kept for hunting, 3 6 % in the rural areas were used for this purpose (Table III).
741
In the urban area (Lagos mainland), 77.6% of the dogs were never confinetí, while
2 2 . 4 % were partly confined (day-time). In the rural areas, only 4 % were partly
confined and 9 6 % of the owned dogs were never confined.
DISCUSSION
The abundance of dogs varies within geographical regions in the same country.
Population density varies with u r b a n and rural habitats, areas of different h u m a n
settlement, and socio-cultural pattern (23). D a t a from the U S A and some countries
in E u r o p e give a dog to h u m a n ratio between 1:10 and 1:6 (23). Rangel et al. (20)
reported ratios between 1:10 and 1:1 in different areas of Mexico City. In the present
study, we recorded a dog to h u m a n ratio of 1:21 in Lagos u r b a n and 1:45 in the rural
areas (ranging from 1:33 to 1:62). Reporting o n the epidemiology of rabies in K a d u n a
State of Nigeria, Ezeokoli et al. (9) noted that incidence varied with dog population
density. In the mainly Christian southern K a d u n a State, the dog to m a n ratio was
between 1:27 and 1:3, while in the mainly Moslem northern part, there was less t h a n
1 dog per 1,000 inhabitants. In general, the ratio of owned dogs to people is greatest
in the more rural regions of a country (23). In the present study, we found the ratio
in rural areas to be double that in the urban area. However, because of the high h u m a n
population density in the u r b a n area, the population density of owned dogs in the
urban area was 8.8 times that of the rural areas.
In developed countries where dogs are kept essentially as pets and companions,
variations in dog population density are directly related to income and economic status
(12). In developing African countries, dog population density is also influenced by
tradition and cultural background as well as the socio-economic activity of the people.
F r o m our survey, it was apparent that while 3 0 % of the dogs are kept as pets, the
growing sense of insecurity occasioned by increasing incidence of violent crimes in
the cities, induce more and more households to own guard dogs. Thus, 4 5 % of owned
dogs in the u r b a n areas surveyed are kept as guards. In the rural areas, dogs are kept
primarily as house guards and as hunting aides (67%). Some renowned local hunters
own two or more hunting dogs. M a n y households in the more remote and traditional
villages keep mongrels as scavengers. In a number of rural communities, including
some of those covered in the survey, dogs are reared and sold for meat. One survey
has shown that areas in Nigeria where dogs serve as a meat source cut across
geographical, religious, and socio-cultural boundaries (8). In some communities, the
dog is prescribed for certain ritual and ceremonial sacrifices and dog meat is chosen
for some traditional festivals. In a few other rural communities, the owning of dogs
is actively discouraged or totally banned by custom and tradition. In these
communities, the dog is perceived as a social nuisance because it is a biting animal
and carries the risk of rabies.
The structure of dog populations in the study areas was evaluated by sex and age
ratios. These data m a y be related to the incidence and spread of a density-dependent
disease such as rabies; it may also serve as a basis for predicting the probable outcome
of dog vaccination campaigns (23). Sex ratios are expressed as the number of males
per 100 females or as a percentage of males, and it is k n o w n that the sex ratio at
birth is 1:1 (23). One survey in central Philippines found the sex ratio of sub-adult
and adult dogs to be nearly equal (3). Other surveys of owned dogs reported a
742
dominance of males. T h e male to female ratio was 2.3:1 in Mexico City (20) and
1.7:1 in rural Ohio (21). In our survey we found the male to female ratio to be nearly
equal, with slight dominance of females (0.9:1 in u r b a n and 0.8:1 in rural areas).
In the absence of an independent and feasible method of age determination, the
analysis of age ratio data was based on information supplied by owners. The mean
age of owned dogs was 2.03 years in u r b a n and 2.3 years in rural areas. In the U S A ,
the mean age of populations of owned dogs was about 4.5 years, while that of pet
dogs captured on the streets was 2.3 years (18, 21). O u r survey showed that 1 1 %
of owned dogs in the u r b a n and 12% in the rural areas were older t h a n 5 years. In
Mexico City, Rangel et al. (20) found that 12% of the dogs were over 5 years. In
the USA, more t h a n one third of the dogs were over 5 years old. Age and sex ratios
have implications for population turnover and survival rates, and also for estimating
annual disease (e.g. rabies) control costs.
Feeding habits and confinement
Feeding of the dogs was related to u r b a n and rural setting, the degree of
confinement or restriction, and the socio-cultural environment. In the u r b a n area,
very few households confine their dogs continuously on a leash. A small proportion
(22%) of the dogs are confined during day time only. Most of the dogs (particularly
the guard dogs) are permitted freedom during the night. The free movement is usually
within fenced premises or a very small home range within the neighbourhood. During
confinement and partial restriction dogs are fed regularly by the owners. The
unrestricted dogs scavenge for food and r o a m the streets and alleys in search of sex
mates.
In the rural areas, where 9 6 % of the owned dogs are never confined, the feeding
pattern is adapted to different local conditions. Owned dogs lead a partly self-sufficient
existence, although they may be irregularly fed by the owners. In the more traditional
communities, there is little demarcation between property lines and residents maintain
a strong sense of communal responsibility (14). In such a setting, most owned dogs
are recognisable or traceable to specific owners, but the dogs enjoy relatively free
range. A dog from one household is permitted to wander the neighbourhood and
may be offered food in other households. The home range of owned dogs in the rural
areas is generally larger or wider t h a n that of u r b a n dogs.
The epidemiological and public health implications of large urban dog populations,
partial restriction in urban areas and free range in the rural areas are apparent. These
factors p r o m o t e straying, encourage the gathering of dogs in packs, and facilitate
easy contact between stray dogs and wildlife. Given the very low vaccination level
observed, there is increased probability of transmission of diseases (especially rabies)
from stray to owned dogs. Certainly, this maintains the cycle of endemic canine rabies.
In addition, there are the problems of environmental pollution, social nuisance of
dog bites, and the hightened h u m a n exposure risk to rabies.
Established parameters for accurate estimation of dog populations are of practical
value in disease control. The questionnaire survey employed in this study does require
further evaluation in new study areas, in more states. The method is economically
and logistically feasible in many developing countries. We should mention that in
the present study we restricted ourselves to assessing the populations of owned dogs.
This is because the proportions or population densities of unowned and stray dogs
may not be established by questionnaire surveys alone. There is need for more extensive
743
pilot studies and national surveys in more African countries. Such major studies could
be sponsored or commissioned by the Inter-African Bureau for Animal Resources
(IBAR), or appropriate agencies of W H O , F A O and O I E in collaboration with local
veterinary and public health authorities and institutions.
*
* *
ÉTUDE PILOTE SUR LA DENSITÉ DE POPULATION ET L'ÉCOLOGIE DES CHIENS
AU NIGERIA. - S.I. Oboegbulem et I.E. Nwakonobi.
Résumé : La dynamique de la population canine est un facteur important de
l'épidémiologie de la rage canine endémique. L'absence d'évaluations fiables
des populations de chiens est une entrave aux campagnes de prophylaxie de la
rage dans les pays en voie de développement, car elle rend impossible une analyse
coût-bénéfice précise des stratégies de lutte. L'OMS, dans ses «Instructions pour
la prophylaxie de la rage canine», a souligné la nécessité des recherches sur la
population et l'écologie des chiens dans les zones urbaines et rurales. Une des
méthodes recommandées consiste à déterminer la densité de la population canine
(chiens/km ) à partir des indicateurs connus de l'abondance des chiens (nombre
de chiens par rapport au nombre d'habitants et à celui des foyers).
2
Les auteurs ont utilisé un questionnaire pour réaliser une étude pilote dans
des zones urbaines et rurales choisies du Nigeria, en vue de déterminer la densité
et la structure de la population des chiens ayant un maître, les différences de
répartition et de densité de population des chiens dans les foyers des zones
urbaines et rurales, ainsi que les facteurs favorisant le vagabondage des chiens
ayant un maître.
Les chiens étaient plus nombreux en zone urbaine qu'en zone rurale. La
relation entre le nombre de foyers possédant des chiens et la localité (urbaine
ou rurale) était hautement significative. La relation entre le nombre de chiens
par foyer et la localité était également significative. Le rapport entre le nombre
de chiens et le nombre d'habitants, en zone urbaine et en zone rurale, a également
fait l'objet d'une étude. Selon ces deux indicateurs, les chiens étaient deux fois
plus nombreux en zone urbaine qu'en zone rurale. La densité de population
des chiens ayant un maître, calculée en fonction du rapport chiens/habitants
et des densités de population humaine, était 8,8 fois plus importante en zone
urbaine (131/km ) qu'en zone rurale (15/km ). L'étude a également porté sur
le rapport mâles/femelles et la répartition par âge pour les chiens des zones
urbaines et rurales.
2
2
Les implications pour l'épidémiologie et la santé publique de populations
canines urbaines importantes, du confinement partiel et de l'élevage en liberté
des chiens ayant un maître dans les communautés urbaines et rurales, comportent
un vagabondage accru, le rassemblement des chiens en bandes, la facilité des
contacts avec les animaux errants et la faune sauvage, et un plus grand risque
d'exposition de l'homme aux morsures de chiens et à la rage.
Du point de vue économique et logistique, la méthode d'enquête utilisée
dans cette étude pilote peut être mise en œuvre dans la plupart des pays en voie
de développement.
MOTS-CLÉS : Chiens - Nigeria - Rage - Statistiques de population.
*
* *
744
ESTUDIO PILOTO SOBRE LA DENSIDAD DE POBLACIÓN Y LA ECOLOGÍA DE LOS
PERROS EN NIGERIA. - S.I. Oboegbulem e I.E. Nwakonobi.
Resumen: La dinámica de la población canina es un factor importante de la
epidemiología de la rabia canina endémica. La ausencia de evaluaciones fiables
de las poblaciones de perros representa un obstáculo para las campañas de
control de la rabia en los países en vías de desarrollo pues imposibilita un análisis
costo-beneficio preciso de las estrategias de lucha. En sus «Instrucciones para
el control de la rabia canina», la OMS ha subrayado la necesidad de las
investigaciones sobre la población y la ecología de los perros en las zonas urbanas
y rurales. Uno de los métodos recomendados consiste en determinar la densidad
de la población canina (perros/km ) a partir de los indicadores conocidos
relativos a la abundancia de perros (número de perros en relación con el número
de habitantes y de hogares).
2
Los autores utilizaron un cuestionario para realizar un estudio piloto en
Nigeria, en zonas urbanas y rurales escogidas de antemano, con el fin de
determinar la densidad y la estructura de la población de los perros que tienen
dueño, las diferencias de repartición y densidad de población de los perros en
los hogares de las zonas urbanas y rurales, así como los factores que favorecen
el vagabundeo de los perros que tienen dueño.
Los perros eran más numerosos en zona urbana que en zona rural. La
relación entre el número de hogares que poseen perros y la localidad (urbana
o rural) era muy significativa, así como también la relación entre el número
de perros por hogar y la localidad. Se estudió además la relación entre el número
de perros y el número de habitantes en zona urbana y en zona rural. Según
estos dos indicadores, los perros eran dos veces más numerosos en zona urbana
que en zona rural. La densidad de población de los perros que tienen dueño,
calculada en función de la relación perros/habitantes y de las densidades de
población humana, era 8,8 veces más importante en zona urbana (131/km )
que en zona rural (15/km ). El estudio también tomó en cuenta la relación
machos/hembras y la repartición por edad para los perros de las zonas urbanas
y rurales.
2
2
Las implicaciones para la epidemiología y la salud pública que representan
poblaciones canicas urbanas importantes, el confinamiento parcial y la cría en
libertad de perros que tienen dueño en las comunidades urbanas y rurales,
incluyen un mayor vagabundeo, el agrupamiento de perros en bandas, la
facilidad de contacto con animales errantes y la fauna salvaje y un mayor riesgo
de exposición del hombre a las mordidas de perros y a la rabia.
Desde el punto de vista económico y logístico, el método de encuesta utilizado
en este estudio puede aplicarse en la mayoría de países en vías de desarrollo.
PALABRAS CLAVE: Estadísticas de población - Nigeria - Perros - Rabia.
*
* *
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