Immunological response to Brucella abortus strain 19 vaccination of cattle in a communal area in South Africa

Brucellosis is of worldwide economic and public health importance. Heifer vaccination with live attenuated Brucella abortus strain 19 (S19) is the cornerstone of control in low- and middle-income countries. Antibody persistence induced by S19 is directly correlated with the number of colony-forming units (CFU) per dose. There are two vaccination methods: a 'high' dose (5-8 × 1010 CFU) subcutaneously injected or one or two 'low' doses (5 × 109 CFU) through the conjunctival route. This study aimed to evaluate serological reactions to the 'high' dose and possible implications of the serological findings on disease control. This study included 58 female cases, vaccinated at Day 0, and 29 male controls. Serum was drawn repeatedly and tested for Brucella antibodies using the Rose Bengal Test (RBT) and an indirect enzyme-linked immunosorbent assay (iELISA). The cases showed a rapid antibody response with peak RBT positivity (98%) at 2 weeks and iELISA (95%) at 8 weeks, then decreased in an inverse logistic curve to 14% RBT and 32% iELISA positive at 59 weeks and at 4.5 years 57% (4/7 cases) demonstrated a persistent immune response (RBT, iELISA or Brucellin skin test) to Brucella spp. Our study is the first of its kind documenting the persistence of antibodies in an African communal farming setting for over a year to years after 'high' dose S19 vaccination, which can be difficult to differentiate from a response to infection with wild-type B. abortus. A recommendation could be using a 'low' dose or different route of vaccination.

Peste des Petits Ruminants Virus Surveillance in Domestic Small Ruminants, Mozambique (2015 and 2017)

Peste des Petits Ruminants (PPR), a transboundary animal disease affecting mainly goats and sheep is caused by a morbillivirus and threatens food security and livelihoods as morbidity and mortality rates can reach 90%. There are no records of PPR in Mozambique, but the disease situation in Tanzania and the ability of PPR virus to rapidly spread across countries constitute a high risk for about 4.7 million goats and sheep in Mozambique. A total of 4,995 goats and sheep were sampled in several provinces during 2015 and 2017 to assess the status of PPR virus (PPRV) in Mozambique and to contribute to surveillance along the border with Tanzania. The sera were screened for anti-PPRV antibodies using a commercial PPR competition ELISA (c-ELISA) and the haemagglutinin based PPR blocking ELISA (HPPR-bELISA). The swabs were tested using one-step RT-PCR for detection of PPRV RNA. The overall percentage of animals with anti-PPRV antibodies by c-ELISA, was 0.46% [0.30–0.70]. However, all the sera positive on c-ELISA were confirmed to be negative by the HPPR-bELISA. Considering that all the swabs were negative for detection of PPRV, no clinical cases were observed during passive surveillance and active sampling, and no symptoms were reported, these results suggest that PPRV is not present in Mozambique.

Animal rabies in Mozambique: a retrospective study with focus on dog rabies and vaccination coverage

Rabies, a highly preventable zoonotic disease, remains a major public health problem in Mozambique with approximately 50 human fatalities per annum due to dog-mediated rabies. This study analysed animal rabies cases and dog vaccination coverage, confirmed between 2001 and 2021, based on history, clinical signs, and/or diagnostic tests. During this period, 955 animal rabies cases were reported with the highest occurrence in Maputo (n = 283; 29.6%) and the lowest from Zambézia and Sofala provinces (n = 30; 3.1%). A significant number of animal rabies cases occurred in 2005 (n = 180; 18.8%). Most cases were identified in domestic dogs (n = 766; 80.2%). During the same period, 4.6 million dogs were vaccinated against rabies and the countrywide coverage was 10.4%. The total number of vaccinations administered increased over the 21-year period, from 46 301 in 2001 to a peak of 464 780 in 2018 before slightly declining in subsequent years. Rabid dogs are still important reservoirs and vectors species in Mozambique. More effective control measures, surveillance, reporting and enhanced awareness programmes are needed to address this neglected disease and consequently meet the global strategic plan to end human deaths due to dog-mediated rabies by 2030.