A Perspective of the Epidemiology of Rabies in South Africa, 1998-2019

Abstract

Despite the implementation of various control strategies aimed at eliminating canine-mediated rabies, the disease is still endemic in up to 150 countries across the world. Rabies remains endemic to South Africa, with various reservoir species (both wildlife species and domestic dogs) capable of maintaining rabies infection, and the epidemiology of the disease is yet to be adequately defined. As such, this study used surveillance data collected between 1998 and 2019 from the two diagnostic laboratories in the country for a statistical space-time analysis to determine regions where significant disease clusters could occur. In addition, the robustness of surveillance activities across the country was evaluated through the mathematical evaluation and visualization of testing rates based on the average number of samples tested per species group. In our study, various significant disease clusters were detected for domestic animals, wildlife and livestock. The significant disease clusters for domestic animals and livestock were primarily restricted to eastern South Africa, while the significant disease clusters in wildlife species were detected across northern and western South Africa. Furthermore, the testing rates identified districts from various provinces where surveillance activities could be considered inadequate, consequently influencing the geographical range of the observed clusters. These results could be used to direct intervention campaigns towards high-risk areas, while also allocating the required resources to improve surveillance in the surrounding areas where surveillance was deemed inadequate.

Keywords: South Africa; epidemiology; rabies burden; spatio-temporal analysis; surveillance.

Figure 1

Number of samples submitted for diagnostic confirmation per province across South Africa between 1998 and 2019.

Figure 2

(A) The total positive rabies cases in South Africa between 1998 and 2019; (B) total negative rabies cases in South Africa between 1998 and 2019; and (C) AAHR values per district across South Africa (2010–2019) where districts below the threshold value are indicated in red.

Figure 3

(A) Positive rabies cases in domestic animals in South Africa between 1998 and 2019; (B) negative rabies cases in domestic animals during the same period.

Figure 4

Significant disease clusters (indicated by the blue hashed lines) for domestic animals in South Africa, 1998–2019.

Figure 5

(A) DAHR testing rates for districts across South Africa (2010–2019) with districts below the defined threshold value indicated in red; (B) significant disease clusters (indicated by the blue hashed lines) for domestic animals with the DAHR values.

Figure 6

(A) the domestic dog densities in km² per district across South Africa, districts below the threshold value are shown in white; (B) the below-threshold DAHR testing rate values (indicated using black hashed lines) in relation to the domestic dog density is indicated as shading on the map.

Figure 7

(A) Positive rabies cases in wildlife species (excluding mongoose species) in South Africa between 1998 and 2019; (B) negative rabies cases in wildlife species (excluding mongoose) during the same period.

Figure 8

(A) Positive rabies cases in mongoose species in South Africa between 1998 and 2019; (B) negative rabies cases in mongoose species during the same period.

Figure 9

Significant disease clusters for wildlife species (indicated by the blue hashed lines) and mongoose species (indicated by the orange hashed lines) across South Africa, 1998–2019.

Figure 10

Species distributions for black-backed jackals (A), bat-eared foxes (B), aardwolf (C), and yellow mongoose species (D). Species distributions adapted using data from the EWT (https://ewt.org.za/red-list/ (accessed on 22 February 2024)).

Figure 11

(A) WHR testing rate values (2010–2019) for each district indicated in green shading with districts that do not have wildlife reservoir species indicated in red hashed lines; (B) significant clusters for wildlife (indicated in blue hashed lines) and mongoose species (indicated in orange hashed lines) indicated in relation to the WHR.

Figure 12

(A) Positive rabies cases in livestock in South Africa between 1998 and 2019; (B) negative rabies cases in livestock during the same period.

Figure 13

Significant disease clusters for livestock in South Africa between 1998 and 2019.

Figure 14

(A) Livestock clusters (indicated by the blue hashed lines) in relation to clusters in domestic animals; (B) significant disease clusters for livestock (indicated by the blue hashed lines) in relation to wildlife clusters.