Title : Effectiveness of autogenous protozoan vaccine against blood protozoa for ruminants
Abstract:
Tropical areas like Bangladesh are endemic for the tick-borne hemoprotozoan diseases babesiosis, anaplasmosis, and theileriosis (BAT). They infect erythrocytes, resulting in output decreases, illness, and mortality that are predicted to cost the world economy more than US$24 billion. While local cow varieties frequently act as asymptomatic reservoirs, exotic and high-yielding cattle types are especially vulnerable. Protozoan growth and outbreak frequency are favored by climate. High-yielding animals frequently do not respond well to current preventative and treatment approaches. To fill a crucial vacuum in control methods, this study aimed to isolate, identify, and characterize BAT species from sheep and cattle in order to aid in the creation and field testing of an autogenous vaccine. In 2020, throughout Bangladesh, 300 blood samples—27 exotic sheep and 273 cattle—were gathered. Giemsa-stained thin blood smears were used for initial screening, and positive samples were collected and combined. From these pools, genomic DNA was isolated, and Babesia, Anaplasma, and Theileria species were identified using a multiplex PCR technique. Based on certain amplicon sizes, PCR verified nine positive pools, identifying species such as Babesia bovis, B. ovis, B. motasi, Anaplasma marginale, A. ovis, Theileria annulata, and T. ovis. The PCR-positive isolates were used to create an autogenous vaccine. After erythrocyte lysis with ammonium chloride, protozoan fragments were extracted, heat-treated to render them inactive, and standardized to a concentration of 1×106 fragments/mL An oil adjuvant was used to emulsify this antigen (1:200 ratio). A 3 mL dosage of the vaccine was administered subcutaneously to exotic sheep. c-ELISA was used to examine 50 serum samples that were collected serially over the course of 24 weeks after vaccination. A strong and persistent humoral immune response was demonstrated by the seroprevalence, which increased from 0% prior to immunization to a peak of 80.50% at week 16. Additionally, from 2021 to 2023, two mechanized exotic cattle farms in Bangladesh received preventive doses of this autogenous BAT vaccination twice a year at doses of 3 mL per adult and 2 mL per calf. No clinical illness outbreaks were documented over this time, suggesting that it may be effective in the field in averting clinical disaster. To sum up, the experimental vaccine produced a significant immunogenic response, confirming its initial effectiveness. To confirm protective immunity, further study using challenge tests and cultivated vaccination seeds is being followed.
