Rift Valley fever (RVf) is a mosquito-borne viral zoonosis showing complex epidemiological patternsthat are poorly understood in South Africa. Large outbreaks occur in the central interior at long, irregular intervals, most recently in 2010-2011; however, the level of herd immunity of ruminant livestock, a key determinant of outbreaks, is unknown. During 2015-2016 a cross-sectional study on 234 randomly-selected farms investigated the prevalence, patterns of, and factors associated with, antibodies to RVF virus (RVFV) in livestock in an area heavily affected by that outbreak. A RVFV inhibition ELISA was used to screen 977 cattle, 1,549 sheep and 523 goats and information on potential risk factors was collected using a comprehensive questionnaire. the estimated RVfV seroprevalence, adjusted for survey design, was 42.9% in cattle, 28.0% in sheep and 9.3% in goats, showing a high degree of farm-level clustering. Seroprevalence increased with age and was higher on private vs. communal land, on farms with seasonal pans (temporary, shallow wetlands) and perennial rivers and in recently vaccinated animals. Seropositivity amongst unvaccinated animals born after the last outbreak indicates likely viral circulation during the post-epidemic period. the current level of herd immunity in livestock may be insufficient to prevent another large outbreak, should suitable conditions recur.Rift Valley fever (RVF) is an arthropod-borne viral zoonosis caused by RVF virus (RVFV), a member of the Phlebovirus genus, family Phenuiviridae of the recently established order Bunyavirales 1 . RVF is endemic primarily in sub-Saharan Africa but has crossed several barriers including the Sahara to Egypt, the Red Sea to the Arabian Peninsula and the Indian Ocean to the Comoros, Mayotte and Madagascar 2-4 . Spread through infected animals and mosquitoes to countries where the disease is not endemic is increasingly possible, with more frequent export of livestock from Africa to other countries and the presence of known or potentially competent vectors in those countries 4,5 . RVFV causes sporadic outbreaks with high morbidity and mortality, characterized by abortion storms and high mortalities in neonatal sheep, cattle and goats 6,7 . Human infection generally occurs concurrently with disease outbreaks in domestic ruminants 2,5,8 , where humans work or live in close contact with livestock.Outbreaks tend to occur following above average rainfall and localized flooding 9 . These climatic conditions favour breeding of floodwater mosquitoes that are the proposed maintenance vectors of this virus via transovarial transmission 10 . The floodwater mosquitoes considered to be vectors on the interior plateau of South Africa are those in the Aedes subgenera Ochlerotatus and Neomelaniconion 11 . Outbreaks may then be amplified by epidemic vectors, of which Culex theileri is considered the most important on the interior plateau 12 . Risk factor studies conducted during and after outbreaks in both humans and animals have identified several other environmental, ...

These cross-sectional reported the occurrence, risk factors, and genetic characteristics of Listeria species recovered from cattle farms and beef abattoirs in Gauteng Province, South Africa. A total of 328 samples collected from 23 cattle farms and 262 samples from 8 beef abattoirs were processed using standard bacteriological and molecular methods to detect Listeria spp. The factors associated with the prevalence of Listeria spp. were investigated, and multiplex polymerase chain reaction (mPCR) was used to determine Listeria species, the pathogenic serogroups, and carriage of eight virulence-associated genes by Listeria monocytogenes. The overall prevalence of Listeria spp. in cattle farms was 14.6%, comprising Listeria innocua (11.3%), Listeria monocytogenes (3.4%), Listeria welshimeri (0.0%) compared with 11.1%, comprising Listeria innocua (5.7%), Listeria monocytogenes (4.6%), Listeria welshimeri (0.8%) for beef abattoirs. Of the three variables (area, type of farm/abattoir, and sample type) investigated, only the sample types at abattoirs had a significant (P < 0.001) effect on the prevalence of L. innocua and L. welshimeri. The frequency of distribution of the serogroups based on 11 L. monocytogenes isolated from farms was 72.7% and 27.3% for the serogroup 1/2a-3a and 4b-4d-4e, respectively, while for the 12 L. monocytogenes isolates recovered from abattoirs, it was 25%, 8.3%, 50% and 16.7% for the serogroup 1/2a-3a, 1/2b-3b, 1/2c-3c, and 4b-4d-4e respectively (P < 0.05). All (100.0%) isolates of L. monocytogenes from the farms and abattoirs were positive for seven virulence genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). The clinical and food safety significance of the findings cannot be ignored.

This study determined the prevalence, risk factors, and molecular characteristics of Listeria species detected in beef and beef products sampled in Mpumalanga province, South Africa. Four hundred beef and beef products were collected from 30 retail outlets in three districts (Bronkhorstspruit, Emalahleni, and Middelburg) within the province. Standard bacteriological and polymerase chain reaction (PCR) assays were used in the study. The overall prevalence of L. monocytogenes and other Listeria spp. in the samples was 8.3% (33/400) and 30% (120/400) (p < .05), respectively. For the five variables investigated, statistically significant effects were evident only for the region (p < .001) and type of product (p < .0001) for L. monocytogenes, the type of outlet (p = .011) and the type of product (p < .0001) for Listeria spp. Of the 20 types of beef and beef products tested, 15 (75%) and 17 (85%) were contaminated by L. monocytogenes and Listeria spp., respectively (p = .429). Among the four categories of products tested, the prevalence of L. monocytogenes was 7.3% (8/109), 10.6% (11/104), 7.5% (8/106), and 7.4% (6/81) for raw beef, ready‐to‐eat (RTE) products, milled beef, and offal & organs, respectively (p > .799). Among the 33 L. monocytogenes isolates, PCR genoserogroup IIa (42.4%, 1/2a‐3a) was most frequently detected. All (100%) of the isolates carried one or more of the eight virulence‐associated genes assessed, with genes inlC and inlJ detected in all the isolates. The overall prevalence of L. monocytogenes (8.3%) and the high frequency of virulent serogroups of L. monocytogenes commonly associated with human listeriosis pose a food safety risk to consumers of beef and beef‐based products contaminated by L. monocytogenes.