Exposure to multiple pathogens: Serological evidence for Rift Valley fever virus, Coxiella burnetii, Bluetongue virus and Brucella spp. in cattle, sheep and goat in Mali

An important problem for livestock production in Mali is occurrence of several infectious diseases. A particular challenge for control of pathogens that affect different species, especially in a system with mixed herds with cattle, sheep and goats. Therefore, this study aimed to investigate co-exposure with Rift Valley fever virus (RVFV), Coxiella burnetii, bluetongue virus (BTV) and Brucella spp. in different livestock species in mixed herds. With the exception of BTV these pathogens are also zoonotic. A retrospective assessment was carried out on a biobank of sera of cattle and small ruminants collected from Sikasso and Mopti regions. Nine hundred and twelve samples from cattle (n = 304), sheep (n = 318) and goat (n = 290) were screened. Serology tests were conducted using commercial kits as per the protocol of the manufacturers. Sero-prevalence for RVFV was 12.8% (Confidence Interval 95%: 9.3–17.1%); 4.7% (2.7–7.7%) and 3.1% (1.4–5.8%) in cattle, sheep and goat respectively. For Coxiella burnetii, the sero-prevalence was 55.3% (49.5–60.9%), 22.6% (18.2–27.6%), and 16.9% (12.8–21.7%); in cattle, sheep and goat respectively; and for BTV sero-prevalence was 88.8% (84.72–92.13%), 51.6% (45.9–57.2%), 56.2% (50.3–62.0%) in cattle, sheep in goat respectively. Brucella sp. had the lowest sero-prevalence and was only detected in cattle and sheep. Regional differences were observed with sero-prevalence of Coxiella burnetii in sheep and goat and BTV in goat being significantly higher in Sikasso than in Mopti (p<0.001). Evidence of exposure to two pathogens in the same animal was most common for the combination Coxiella burnetii and BTV in cattle (51.6%), followed by sheep (17.0%) and goat (15.5%). Considering the scarcity of disease occurrence and epidemiological data in most sub-Saharan countries including Mali, this multi-pathogen survey provides important evidence that cattle, sheep and goat are exposed to pathogens that may negatively impact productivity and pose a risk for public health. The results from this study highlight the urgent need for a better understanding of pathogen diversity and their impact on human and animal health in order to minimize resulting risks. Given that some of the pathogens investigated here are zoonotic, establishment of One-Health surveillance system to monitor disease in animals and people is warranted and intersectoral collaboration is recommended

Evaluation of a candidate thermotolerant vaccine against peste des petits ruminants in Mali

Objective The objective of this study was to evaluate the thermotolerance profile of a PPR vaccine protocol developed by ILRI and transferred to the LCV (lot ILRI 005ND) under laboratory and field conditions. Methods The attenuated PPRV 75/1 LK6 BK2 Vero70 strain was used as a production antigen with Lactalbumin hydrolysate-sucrose (LS) as stabilizers and vero cells used as host cells in the multiplication of the viral strain. The formed vaccine fluid was divided into a 2 ml per vial/100 doses. The freeze-drying was carried out according to the ILRI protocol during 62h50mn following 20 steps. The final titre of the vaccine was 105.66 TCID50. The quality of the vaccine lot ILRI 005ND, as well as its thermostability profiles have been tested by the PANVAC under the QCR1731, reference N°P188/709/58/20 of 08 January 2021. In the laboratory, the thermotolerance of the vaccine was evaluated at the LCV under three scenarios for 14 days: Scenario A: under ice (+4°C to +8°C) Scenario B: room temperature (32.5°C to 38.5°C) Scenario C: under incubation at 40°C and 45°C. In the field, 626 serum samples were collected from sheep and goats in three villages in Koutiala region. These sera were subject to two successive PPR serological tests to ensure they were negative. The vaccine was then reconstituted with 500 ml of sodium chloride solute 0.9% before use on animals. Scenario 1: 284 animals were vaccinated after 3 to 5 days of vaccine stored at ambient temperature during transport from the laboratory in Bamako to the field (395 Km) (+21.5°C to +34.8°C), storage on site (± 25 °C) and field for vaccination (maximum exposure + 51°C). Scenario 2: 162 animals were vaccinated after 6 to 7 days of vaccine having undergone thermal shocks with freezing storage temperature (-20 °C), storage on site (±33°C) and maximum field exposure (+47 °C). Scenario 3: 180 animals were vaccinated after 8 to 9 days of vaccine stored permanently under cold chain from the laboratory to the feet of the animal (-18°C to +19°C). Results In the laboratory after 14 days, with an initial vaccine titre of 105.66 TCID50 Scenario A: titre was 105.45 TCID50 Scenario B: titre was 103.80 TCID50 Scenario C: titres were 104.30 TCID50 at 40°C but less than 102.5 (minimum required) at 45° C In the field at one month post vaccination Scenario 1: 97.88% seroconversion Scenario 2: 98.76% seroconversion Scenario 3: 99.44% seroconversion No significant difference was observed in seroconversion between the tree lots (X-squared=1.9488; p-value =0.3774) Conclusion The vaccine maintained a satisfactory titre under different thermostability profiles in the laboratory. Sero-conversion rates in the field after vaccination was also good . The next step is to carry out sero-neutralization assays on the collected serums to measure protection rates of animals

Integrated approach to facilitate stakeholder participation in the control of endemic diseases of livestock: The case of peste des petits ruminants in Mali

In Mali, small ruminants (SRs) are an important means for enhanced livelihood through income generation, especially for women and youth. Unfortunately, opportunities for livestock farmers to tap into these resources for economic growth are hindered by high burden of endemic diseases such as peste des petits ruminants (PPR). A key component for the control of PPR is vaccination of SRs. However, low participation of farmers to vaccination was identified by stakeholders of the livestock value chains as a key constraint to successful vaccination programs. This study was implemented in the framework of a project which aimed at improving the domestic ruminant livestock value chains in Mali by upscaling proven interventions in animal health, feeds and feeding and livestock marketing. The objectives of the study were to review the context of livestock vaccination in Mali and evaluate the impact of innovation platforms (IP) as a means for engaging stakeholders in the vaccination process. Desk review, key informant interviews (KII) and net-mapping were used to understand the context of livestock vaccination, while vaccination coverage and sero-monitoring together with group interviews were used to measure the impact of the intervention. IPs were created in 24 communes in three regions: 15 IPs in Sikasso, 4 IPs in Mopti and 5 IPs in Timbuktu. They developed work plans and implemented activities focusing on improving interaction among key vaccine chain delivery stakeholders such as farmers, private veterinarians, vaccine manufacturers, local leaders and public veterinary services; involving them in the planning, implementation and evaluation of vaccination programs and fostering knowledge sharing, communication and capacity building. After 2 years of implementation of IPs, vaccination coverage for SRs increased significantly in target communes. During the first year, seroprevalence rate for PPR increased from 57% (CI95: 54–60%) at baseline to 70% (CI95: 67–73%) post-vaccination in Sikasso region, while in Mopti region, seroprevalence increased from 51% (CI95: 47–55%) at baseline to 57% (CI85: 53–61%) post-vaccination. Stakeholder engagement in the vaccination process through facilitated IPs was successful in fostering participation of farmers to vaccination. However, a sustainable vaccination strategy for Mali would benefit from consolidating the IP model, supported by Government investment to strengthen and adjust the underlying public-private-partnership