RESUMO
A study was conducted to determine the seroprevalence and risks factors of Coxiella burnetii in zebu cattle from the northern regions of Cameroon. From a total of 2016 (1754 females and 262 males) sera sampled, 801, 762 and 453 were collected, respectively, from Adamawa, North and Far North, and screened for Coxiella burnetii using indirect enzyme-linked immunosorbent assay (iELISA). A total of 23.76% (479/2016) were serologically positive. The seroprevalence of Adamawa, North and Far North were 29.09% (233/801), 19.95% (152/762) and 20.75% (94/453); respectively. The seropositivity of male and female were 4.58% and 26.62%; respectively. Cattle from Adamawa region were more likely to have been exposed to C. burnetii than animals from Far North region (OR = 3.28; 95%CI: 1.13-7.85; p = 0.02). The Gudali breed was significantly more infected than Aku (OR =2.52; 95%CI: 1.06-5.99; p = 0.03), and animals aged of (6-9) years were 1.89 times more likely to have been infected to C. burnetii than young animals (p = 0.03). The seropositivity to this bacterium was significantly associated to pregnant cattle than non-pregnant (OR = 1.71; 95%CI: 1.01-2.90; p = 0.04). Female cattle were more likely to have been infected by C. burnetii than male and the rainy season were 1.66 more associated to this disease than dry season. The linear regression model indicated that C. burnetii seropositivity were positively correlated to the regions (0.09, CI: 0.04; 0.18; p = 0.007), age (0.01, CI: -0.01; 0.04; p = 0.02), sex (0.19, CI: 0.08-0.32, p = 0.001) and physiological status (0.11, CI: -0.04; 0.26; p = 0.006). This study revealed that C. burnetii infection is widespread among zebu cattle of Adamawa, North and Far North of Cameroon.
RESUMO
Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, is a neglected tropical disease mainly of sub-Saharan Africa. Worldwide, an estimated 20.9 million individuals live with infection and a further 205 million are at risk of disease. Current control methods rely on mass drug administration of ivermectin to kill microfilariae and inhibit female worm fecundity. The identification and development of efficacious vaccines as complementary preventive tools to support ongoing elimination efforts are therefore an important objective of onchocerciasis research. We evaluated the protective effects of co-administering leading O. volvulus-derived recombinant vaccine candidates (Ov-103 and Ov-RAL-2) with subsequent natural exposure to the closely related cattle parasite Onchocerca ochengi. Over a 24-month exposure period, vaccinated calves (n = 11) were shown to acquire infection and microfilaridermia at a significantly lower rate compared to unvaccinated control animals (n = 10). Furthermore, adult female worm burdens were negatively correlated with anti-Ov-103 and Ov-RAL-2 IgG1 and IgG2 responses. Peptide arrays identified several Ov-103 and Ov-RAL-2-specific epitopes homologous to those identified as human B-cell and helper T-cell epitope candidates and by naturally-infected human subjects in previous studies. Overall, this study demonstrates co-administration of Ov-103 and Ov-RAL-2 with Montanide™ ISA 206 VG is highly immunogenic in cattle, conferring partial protection against natural challenge with O. ochengi. The strong, antigen-specific IgG1 and IgG2 responses associated with vaccine-induced protection are highly suggestive of a mixed Th1/Th2 associated antibody responses. Collectively, this evidence suggests vaccine formulations for human onchocerciasis should aim to elicit similarly balanced Th1/Th2 immune responses.
