In the original publication [...].
A shift from synthetic chemical nematicides to bionematicides in plant protection has led to the development of Nemarioc-AL and Nemafric-BL phytonematicides to manage plant parasitic nematodes. However, there is a lack of information on the accumulation of cucurbitacin residues and the cytotoxicity of phytonematicides on non-target entities. The aims of the study were to determine the cucurbitacin residue accumulation after the application of Nemarioc-AL and Nemafric-BL phytonematicides in tomato fruits and to determine their cytotoxic effects on a eukaryotic (Raw 264.7 cell line) model system. Two separate trials for Nemarioc-AL phytonematicide and Nemafric-BL phytonematicide, each applied at 3%, were conducted concurrently on sandy loam, dark soil, red soil, silt soil, sandy soil, and sandy loam (+). Each trial was arranged in a randomized complete block design (RCBD) and replicated six times. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) viability assay was used to assess the cytotoxicity of Nemarioc-AL and Nemafric-BL phytonematicides, and the Annexin-V and DAPI apoptosis assay was performed on Raw 264.7 macrophage cells. In Nemarioc-AL phytonematicide-treated soil type, the highest accumulation of cucurbitacin B residues in fruits was observed on sandy loam (+) (37.1 ng/g), followed by red soil with 27.0 ng/g and then sandy soil with 21.7 ng/g, and dark soil showed the least at 20.3 ng/g. The phytonematicides were non-toxic at lower concentrations, ≤1.25 mg/mL. However, the higher concentrations (>1.25 mg/mL) of phytonematicides exhibited cytotoxic effects on the Raw 264.7 cell line, with 50% cell viability in comparison with curcumin (100 μM). The IC50 values for Nemarioc-AL and Nemafric-BL phytonematicides on Raw 264.7 cell lines were 0.55 and 1.6 mg/mL, respectively. Similar to the MTT viability assay, the Annexin-V and DAPI apoptosis assay did show that the low concentrations of phytonematicides (0.313 mg/mL) had no signs of apoptosis or necrosis; however, high concentrations (10 mg/mL) had signs of apoptosis as opposed to necrosis. Therefore, the products can be used at lower concentrations to manage nematodes and avoid the toxicity of the products.
Brucellosis is a zoonotic pathogen of livestock, wildlife and humans, with significant implications for reproductive losses and public health. The movement and introduction of breeding animals with unknown status into previously Brucella-negative herds pose a risk for disease introduction and sustained transmission. This case study documents two independent brucellosis outbreaks integrating epidemiological observations with serial serological testing, bacteriological culture and molecular confirmatory assays following abortion events. Diagnostic tests were performed, including serology, PCR and culture from diverse samples. On a cattle farm, animals previously certified as brucellosis-negative demonstrated progressive seroconversion from 2024 onwards. Brucella abortus was detected in the blood clots of tested animals using abortus-melitensis-ovis-suis PCR (AMOS-PCR), including a suspect bull that later tested seronegative on follow-up serology. A Brucella-positive human case occurred following direct exposure to the infected cattle farm, underscoring the zoonotic risk. On the sable antelope farm, B. abortus was detected in two seropositive females through culture of lymph nodes and amniotic fluid, while B. abortus was also isolated from the semen of a seronegative breeding bull, suggesting that the bull was a carrier and posing a transmission risk to the herd. The findings demonstrate that infected breeding males may remain seronegative while actively harbouring and shedding B. abortus. This study indicates that seronegative breeding males can undermine brucellosis control programmes, may act as undetected reservoirs of infection, thereby challenging current surveillance strategies. The findings highlight the diagnostic limitations of relying solely on serological tests, particularly in chronically infected cattle and wildlife, and support the integration of more sensitive assays, such as iELISA, alongside PCR methods, into diagnostic strategies on brucellosis-affected farms to improve detection and support eradication efforts. Contribution: Strengthened biosecurity, systematic testing of breeding males, and comprehensive vaccination programmes are critical to preventing ongoing spillover among livestock, wildlife, and humans in South Africa.
In East and Southern Africa, the African swine fever (ASF) virus is maintained in an ancient sylvatic cycle involving warthogs (Phacochoerus spp.) and Ornithodoros soft ticks inhabiting warthog burrows. Although carbon dioxide (CO2) traps have previously been used to collect ticks from pigsties in Portugal, this method has never been tested in the context of the ASF sylvatic cycle in Africa. As warthogs adapt their resting site preferences in response to different levels of habitat transformation, our study aimed to evaluate the effectiveness of CO2 traps versus traditional manual collection of soft ticks inhabiting two warthog resting sites: warthog burrows (natural) and house decks (anthropogenic). The study was performed in Mjejane Game Reserve, a wildlife conservancy adjacent to the Kruger National Park in South Africa. Sixty-one warthog resting sites (31 natural burrows and 30 house decks) were sampled to compare Ornithodoros tick numbers using manual and CO2 trap methods during wet (summer) and dry (winter) seasons. The number of ticks collected with CO2 traps (n = 2024) was significantly higher than those collected with the manual method (n = 885, P < 0.001) for both resting site types. Moreover, the number of ticks collected using CO2 traps from house decks (n = 1399) was significantly higher (P < 0.001) compared to burrows (n = 625). There were no differences in the number of ticks collected between seasons. Our results suggest that CO2 traps are highly efficient for collecting Ornithodoros ticks from the two warthog resting site types evaluated in our study area. They also confirm that warthogs can adapt to different levels of habitat transformation and human presence. The standardised use of the CO2 trap method facilitates investigations on the distribution of tick-related ASF cycles in sub-Saharan Africa and improves our understanding of the eco-epidemiology of ASF and other Ornithodoros tick-borne diseases.
