Surveillance of the rabies-related lyssavirus, Mokola in non-volant small mammals in South Africa

Molecular Characterization of Lyssaviruses Originating from Domestic and Wild Cats Provides an Insight on the Diversity of Lyssaviruses and a Risk of Rabies Transmission to Other Susceptible Mammals and Humans in South Africa

Rabies is one of the most significant public and veterinary health problems, causing approximately 59,000 human deaths annually in the developing countries of Asia and Africa. The aetiologic agent, a viral species of the Lyssavirus genus, is highly neurotropic and has a wide host range, including terrestrial mammals and several Chiropteran species. The Lyssavirus mokola (MOKV) was first isolated in the late 1960s from organ pools of shrews (Crocidura flavescens manni) in the Mokola forest (Nigeria). To date, at least 30 MOKV isolations have been confirmed, all exclusively from Africa, with 73% from southern Africa. There is limited knowledge about the epidemiology of MOKV, and the reservoir host species is unknown. Here, we report on the molecular characterization of rabies viruses originating from both domestic and African wild cats. A partial region of the lyssavirus genome, encoding the nucleoprotein, was amplified and sequenced. Nucleotide sequence analysis demonstrated that 98% of cats were infected with both the canid and mongoose rabies virus variants, as well as a rare lyssavirus, Lyssavirus mokola, from a domestic cat from Eswatini. Furthermore, the nucleotide sequence divergence between the recently identified MOKV isolate and the historical Lyssavirus mokola isolates ranged from 6.8% to 8.3%. This study further highlights the association between the potential host species of Lyssavirus mokola and the domestic cat as an incidental host, and the important role cats may play in rabies transmission dynamics in the country. Therefore, continuous vaccination of domestic cats against rabies is crucial, even after the elimination of dog-mediated rabies, as spillover related to sylvatic rabies cycles is likely to occur.

Ecological interactions, local people awareness and practices on rodent-borne diseases in Africa: A review

Several anthropogenic activities exposure humans to the risk of rodent-borne diseases. These activities are but not limited to logging, clearing land for crop cultivation, and consuming rodents. Rodents are a highly diverse mammalian group and harbor many zoonotic diseases. This review focuses on dominant rodent-flea species, rodent-borne zoonotic diseases and awareness and management practices against rodent-borne diseases in Africa. Relevant academic literature spanning from 1974 to 2021 was analysed. Dominant rodent species reported in Africa included:- Mastomys natalensis and Rattus rattus, while dominant flea species included Xenopsylla brasiliensis and Xenopsylla cheopis. Rodents were reported as hosts to a wide range of parasites which can be passed to humans. Rodents were also reported as hosts to some protozoans, trematodes, cestodes, nematodes, bacteria and viruses which are transmissible to humans. Some studies conducted in West Africa revealed good knowledge and practices on plague and Lassa fever diseases among respondents, whereas other studies reported poor practices on Lassa fever management. In part of Southern Africa, some studies reported poor knowledge and practices on plague disease. Further research on rodent-borne disease awareness and management strategies in African countries is desirable.

Host-Associated Distribution of Two Novel Mammarenaviruses in Rodents from Southern Africa

Mammarenaviruses are hosted by several rodent species, a small number of which have been known to be zoonotic. Host surveillance among small mammals has identified a large diversity of previously undescribed mammarenaviruses. Intensified biosurveillance is warranted to better understand the diversity of these agents. Longitudinal host surveillance involving non-volant small mammals at a site in the Limpopo province, South Africa, was conducted. The study reports on the screening results of 563 samples for the presence of mammarenavirus RNA. PCR-positive samples were subjected to sequencing using Miseq amplicon sequencing. Sequences with close similarity to Mariental and Lunk viruses were identified from two rodent species, Micaelamys namaquensis and Mus minutoides. This represents the first description of these viruses from South Africa. The genomic sequences reported here partially satisfied the requirements put forward by the International Committee on the Taxonomy of Viruses' criteria for species delineation, suggesting that these may be new strains of existing species. The known distribution of these mammarenaviruses is thus expanded further south in Africa.

Lyssaviruses and the Fatal Encephalitic Disease Rabies

Lyssaviruses cause the disease rabies, which is a fatal encephalitic disease resulting in approximately 59,000 human deaths annually. The prototype species, rabies lyssavirus, is the most prevalent of all lyssaviruses and poses the greatest public health threat. In Africa, six confirmed and one putative species of lyssavirus have been identified. Rabies lyssavirus remains endemic throughout mainland Africa, where the domestic dog is the primary reservoir - resulting in the highest per capita death rate from rabies globally. Rabies is typically transmitted through the injection of virus-laden saliva through a bite or scratch from an infected animal. Due to the inhibition of specific immune responses by multifunctional viral proteins, the virus usually replicates at low levels in the muscle tissue and subsequently enters the peripheral nervous system at the neuromuscular junction. Pathogenic rabies lyssavirus strains inhibit innate immune signaling and induce cellular apoptosis as the virus progresses to the central nervous system and brain using viral protein facilitated retrograde axonal transport. Rabies manifests in two different forms - the encephalitic and the paralytic form - with differing clinical manifestations and survival times. Disease symptoms are thought to be due mitochondrial dysfunction, rather than neuronal apoptosis. While much is known about rabies, there remain many gaps in knowledge about the neuropathology of the disease. It should be emphasized however, that rabies is vaccine preventable and dog-mediated human rabies has been eliminated in various countries. The global elimination of dog-mediated human rabies in the foreseeable future is therefore an entirely feasible goal.