Date Published: February 15, 2019
Publisher: F1000 Research Limited
Author(s): Austine O Bitek, Eric Osoro, Peninah M Munyua, Mark Nanyingi, Yvonne Muthiani, Stella Kiambi, Mathew Muturi, Athman Mwatondo, Rees Muriithi, Sarah Cleaveland, Katie Hampson, M. Kariuki Njenga, PM Kitala, SM Thumbi.
Background: Rabies causes an estimated 59,000 human deaths annually. In Kenya, rabies was first reported in a dog in 1912, with the first human case reported in 1928. Here we examine retrospective rabies data in Kenya for the period 1912 – 2017 and describe the spatial and temporal patterns of rabies occurrence in the country. Additionally, we detail Kenya’s strategy for the elimination of dog-mediated human rabies by 2030.
Every year rabies is estimated to kill around 59,000 (95% CI: 25-159,000) people globally, with the vast majority of rabies deaths occurring in rural Africa and Asia
2. Additionally, the disease is estimated to cause over 3.7 million (95% CI: 1.6–10.4 million) disability-adjusted life years (DALYs) and 8.6 billion USD (95% CI: 2.9–21.5 billion) in economic losses annually
1. These human and economic losses occur despite the existence of effective anti-rabies vaccines for humans and animals and data that supports the feasibility of dog-rabies elimination
4. In areas with high canine rabies burden, human rabies remains largely underreported owing to poor surveillance and misdiagnosis with other common diseases manifesting with nervous disorders such as cerebral malaria
7. Consequently, this has led to a perceived lack of importance for human rabies, driving a cycle of neglect for this endemic disease
We computed the proportions of human and animal samples submitted that tested positive for rabies by year, number of cases by species and administrative counties and examined spatial and temporal trends in rabies occurrence. We determined the proportion of samples submitted that were positive for rabies by year and for each county. Linear mixed-effect models with year as the fixed effect, and the county as a random effect (to account for proximity to testing laboratories) were used to test if the proportion of submitted samples that were positive for rabies changed over time. The analysis was carried out using
R platform (version 3.4.0) for statistical computing
Between 1958 and 2017, 7,584 samples from suspect human and animals rabies cases were submitted for laboratory testing. Samples from domestic animals (cattle, dogs, sheep, goats, pigs and equine) accounted for 93% (7,013/7,584), wildlife (jackal, fox, mongoose, lions, squirrels, bats, and civet) for 5% (407/7,584) and those from humans for 2% (164/7,584) of the total samples (
Analysis of the number of human and animal samples submitted and confirmed for rabies shows three periods with distinct patterns of rabies occurrence. First is the period from 1958 to the early 1970s where a relatively low number of cases were reported (<50 cases/year). The second is the period covering the 1980’s and the early 1990’s where more than >200cases were reported per year. The third period covers the mid 1990s to 2017 with approximately 100 confirmed cases reported per year (
Figure 1). Analyses of the percent positivity data show a general increase over time in the proportion of samples submitted that were positive for rabies (
Figure 2). The model estimates were 0.38 (95% CI 0.17, 0.59) increase in percent positivity per year. Over time, most positive cases were consistently confirmed in domestic animals, with the majority being domestic dogs (
Historical records show the first case of rabies was in a dog reported in the outskirts of Nairobi in 1912, and the first human case in a woman from the Lake Victoria region in 1928. Our data shows the reported cases were relatively low in numbers and confined to less than 10% of the counties until outbreaks that occurred in the 1940s and 1950s (
Figure 4). Up until 1970, less than half of the counties were reporting rabies cases, and the proportion of samples found positive for rabies was low. The high number of confirmed cases observed in the 1980’s (
Figure 1) was accompanied by increased geographical spread of the disease affecting more than half the counties. Since the 1980’s over 85% of counties in Kenya have consistently reported confirmed cases of rabies (
Figure 4). Cumulatively, 6 of 47 counties (Nairobi, Machakos, Nakuru, Kiambu, Nyeri and Kericho) accounted for nearly two-thirds of all samples submitted and those found positive for rabies (
Figure 5). Each of the six counties has either a veterinary laboratory that carries out FAT or is adjacent to a county with A laboratory with capacity for rabies testing.
Here we have examined data from passive surveillance for rabies in humans and animals in Kenya for the period 1912 – 2017. Although the first official records of the disease date back to 1912, a decade after the establishment of the veterinary department in Kenya, rabies was likely present earlier as local communities in South Nyanza already used the name “swao” to refer to rabies in dogs and jackals
17. We were unable to find any literature on the historical emergence of rabies in Kenya, but phylogenetic analysis of rabies viruses in Tanzania show the circulation of two major genetic lineages one of which is thought to have originated from Kenya
The data underlying this study is available from Open Science Framework
http://doi.org/10.17605/OSF.IO/B6WKR35. It contains two datasets – dataset 1: “KenyaRabiesData1958to2017.csv” that produces
Figure 3 and
Figure 5 and dataset 2: “100YearsRabiesData.csv” that produces
Figure 4. The R codes used are provided in a file named “Rcodes_100yearsRabiesinKenya.R”. These datasets are available under a CC0 1.0 Universal license. No records of samples submitted were available for the years 1995, 1996 or 1997.