Spatio-temporal epidemiology of dog bite injuries at Kakamega Provincial

Hospital, KenyaKelly A Nelima1, Mark O Nanyingi 2, 3§, Gideon M. Kikuvi4, Willis Akhwale5, Jared Omolo6

1Ministry of Livestock and Development, Provincial Veterinary Office, PO BOX 871, Kakamega, Kenya

6 Field Epidemiology and Laboratory Training Program, US Center for Disease Control , Kenya

2 Ministry of Livestock and Development, District Veterinary Office, PO BOX 60 -50135, Khwisero, Kenya,

3 Kenya Scientific Analysts, P.O. Box 531-00202, Kenyatta National Hospital, Nairobi, Kenya,

4Jomo Kenyatta University of Agriculture and Technology, Box 3249-00200, Nairobi, Kenya

5 Ministry of Public Health and Sanitation, Kenya

6 Field Epidemiology and Laboratory Training Program, US Center for Disease Control , Kenya

§Corresponding author : mnanyingi@gmail.com

44TH KVA ANNUAL SCIENTIFIC CONFERENCE , APRIL 2010

ALMOND RESORT, GARISSA KENYA

THEMATIC SESSION : ZOONOSES

BACKGROUND • ETIOLOGY OF BITES: Dog bites result from imperfect relationship between humans and animals. These can result in physical and psychological trauma, wound infections, septicemia, rabies and death (Sinclair and Zhou, 1995).

• EPIDEMIOLOGICAL TRIAD

•

• EPIDEMIOLOGICAL BURDEN : Dog bites are a significant public health problem due to mortality and morbidity (DALYS, YLL).

• REEMERGING /EMERGING INFECTIOUS DISEASES: Zoonoses (Rabies),

• Dogs are recognized to play a role in about 100 zoonotic diseases (WHO, 1987; WHO/WSPA, 1990).

RABIES • Prehistoric: Transmissibility before germ theory (Pasteur, 1885)

• Lyssavirus (negative sense Rhabdovirus, ss RNA)

• • Enzootic dog-to-dog transmission (R0)

• Dog-to-Human Rabies Transmission.

• Fatal neurological disease in humans : Acute, progressive encephalomyelitis

• Public Health Burden , Economics

• Prophylaxis: human prophylactic and postexposure vaccination , PET (RIG)

• Interventions: passive-canine rabies-surveillance, central point vaccination, dog population reduction(baiting, castration)

Rabies Global Distribution: Genotype and Endemicity (2007)

Africa 1b (Dog)

Human Rabies Deaths Global Distribution (2003)

RESEARCH QUESTION ?

• Endemic canine rabies is a reemerging neglected zoonosis often underestimated in Kenya but remains a public health and economic burden to the rural poor.

•Understanding the transmission dynamics and spatial distribution of dog bites over specified time period can assist in assessment of risk factors, design of interventions to exposure and the estimation of rabies burden

59.5%

40.5%

83%

10%

5%

2%

Kaare at al, 2009

1. To identify, spatially and temporally, high-risk zones of dog bites by specifically identifying; •a) The population at risk •b) Environmental & socio-economic risk factors.

2. Evaluate changes in this risk over time. in order to assist in planning in establishment of rabies vaccine clinics .

AIMS OF STUDY

METHODOLOGY

Location: Kakamega District, Western Kenya(1,395 Km2 )Demographics: 603,422 persons in 1999Site : Kakamega PGH(L5), ~ 4MReferal Environmental variables: Forests, Rivers, SugarcaneDesign : Cross-sectional (2009) & Retrospective (2006-2008)Sampling : Multiphase (148 bites)Inclusion: All consenting/confirmed dog bite patients Exclusion: Non consenting patients Data collection: Semi-structured questionnaire(socio-demographics, management), Pictures.Spatial analysis: GPS coordinates and GIS distribution mappingData analysis: Univariate /bivariate analysis, OR,Ethical approval : NCST , JKUAT,MOH,MOLD

RESULTS: SPATIAL DISTRIBUTION

• Spatial-temporal clustering of dog bites showed irregular pattern of spread with declining incidence rates from the periurban center.

• Irregular dispersal pattern and clustering due to: • Reporting determined by accessibility and distance from

hospital influenced by semipermeable barriers (roads, rivers, forests , sugarcane).

• • Presence of other medical facilities. (negative)

• Affordability and access to medicare by urban population(An association of increased risk for canine rabies and areas of low socio-economic status).

• Lower vaccination coverage and increased densities of unrestrained dogs are strongly associated with poorer distant urban and rural areas.

DISCUSSION :

• Patterns of bites may be strongly associated with other measures of animal habitat and physiographic barriers that form corridors for animal movement such as forests and rivers.

• We suspect that these patterns may emerge from simulations on heterogeneous landscapes using ecologically defined areas with a finer spatial resolution of the landscape.

• Variables such as human population density may provide more information when the spatial distribution of humans is modeled at a finer spatial resolution than the township average .

HYPOTHESIS H0, Bd ≥Ev Ha, Bd ≠Ev

RETROSPECTIVE BURDEN ANALYSIS

N= 6829, incidence rise= 7.9% (p < 0.001.)Seasonal variation due to human-dog density and socioeconomic dynamics.Bimodal peaks correlated with breeding seasons

Temporal trends of Animal Bites at Kakamega PGH 2006-2008.

•148 dog bite incidents with children below 10 years being more involved (33.8%).

•Most bites occurred on the lower extremities 124/148 (83.8 %).

•1.0% of bites resulted in rabies and death after PET.

•The retrospective analysis revealed a temporal increase in prevalence 7.9 % (P<0.05). (N= 6829).

•Seasonal clustering in March and August with a mean monthly bite incidence of 22.44% ,strongly associated with the breeding seasons of dogs hence increased aggressiveness

•2008 had the highest mean monthly incidence of 30%

DESCRIPTIVE STATISITCS AND CLUSTERING EFFECT

• Annual increase in reporting can be attributed to increased public sensitivity and awareness to Rabies through the veterinary department..

• The trend reflects the probable range with the given data, but the true level may actually be even higher because of lack of accurate denominator data

• Clustering may be significant in isolation or purely a random phenomenon.

• • The map indicates that vaccination clinics (CPV) could

be effective if they were spatially targeted(Lubao).

• Disparities in the affordability and accessibility of post-exposure treatment and risks of exposure to rabid dogs result in a skewed distribution.

EPIDEMIC FOCI INTERRUPTION MODEL

The vaccination coverage falls below the target 70% of population with increasing distance from the central point vaccination clinics. Hence location can be determined in consideration of human-dog densities.

Kaare at al, 2009

HOSPITAL

RABIES VACCINE CENTER

LUBAO

Vaccine coverage Vs distance

• Lack of a reliable relational database in public hospitals

• Inaccurate denominator population influencing the accuracy of disease estimates.

• No laboratory confirmatory diagnosis of the status of dogs.

• Genetic determination of circulating strain

• Wildlife populations reservoirs ignored due to logistical challenges possible infection spillover.

CAVEATS

• Active animal bite surveillance studies are required to improve the estimates of the true burden of rabies in peri-urban settings

• These methods should prove valuable in modeling disease dynamics where local propagation is affected by local geography.(Monte carlo simulation & Knox’s test )

• Small-scale active case detection studies are a good basis for improving regional and national-level estimates of rabies morbidity and mortality.

• Use of spatial models to generate risk maps may be useful in formulation of specific plans to manage or control disease.

• Although the current analyses are descriptive , they provide a basis for further epidemiological investigations into the spatio temporal aspects of the rabies endemicity. We hope that others may find this approach useful for application to other infectious disease systems.

CONCLUSIONS

• Acosta-Jamett et al ., 2010. Demography of domestic dogs in rural and urban areas of the Coquimbo region of Chile and implications for disease transmission. Prev Vet Med. ?????

• Kaare et al ., 2009. Rabies control in rural Africa: Evaluating strategies for effective domestic dog vaccination. Vaccine. 27. 152-160

• Ichhpujani et al ., 2008. Epidemiology of animal bites and rabies cases in India. A multicentric study. J Commun Dis.40(1):27-36

• Ostfeld et al ., 2005. Spatial epidemiology: an emerging (or re-emerging) discipline. TRENDS in Ecology and Evolution ??20 .6

• Knobel et al ., 2005. Re-evaluating the burden of rabies in Africa and Asia. Bull World Health Organ. 83(5):360-8.

• Fe`vre et al ., 2005. The epidemiology of animal bite injuries in Uganda and projections of the burden of rabies. Tropical Medicine & International Health. 10 (8) 790 – 798

BIBLIOGRAPHY

•DVO- (Kakamega Central , North, East), Butere•Director of Veterinary Services.•Director of Medical Services •Provincial Director of Veterinary Services(W)•Medical Superintendent and Staff KPGH •Study Participants • Reviewers (Dr. Thumbi)

ACKNOWLEDGEMENTS