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. 2023 Feb 28;78(1):369-378.
doi: 10.22092/ARI.2022.359002.2352. eCollection 2023 Feb.

Serological and Molecular Detection of Human Brucellosis in Rural Areas in Wasit Province, Iraq

K Alqaseer  1 , A A M Al-Khafajy  2 , E A K Almkhadhree  2
Affiliations

Serological and Molecular Detection of Human Brucellosis in Rural Areas in Wasit Province, Iraq

K Alqaseer et al. Arch Razi Inst. .

Abstract

Brucellosis is endemic in Iraq, and annual surveys using advanced diagnostic assays are needed. This study aimed to investigate the prevalence of human brucellosis in rural areas in Wasit province using ELISA and PCR. A total of 276 serum samples were randomly obtained from participants from rural areas in the Wasit province. The results showed that out of 276 serum samples tested by ELISA, 30.07% were positive. Significantly, mild infection was increased compared to moderate, severe and highly severe infections. To confirm the species of Brucella, seropositive samples were tested by PCR assay targeting the BCSP31 gene for Brucella spp. and the IS711 gene for B. abortus and B. melitensis. Molecular findings confirmed 30.12% positive samples to Brucella spp., including 28% and 44% positives to B. abortus and B. melitensis, respectively, whereas 28% positive samples to other undifferentiated species of Brucella. Association between seropositivity and demographic risk factors, age and gender, were reported to be significantly higher among individuals aged 21-40 (41.91%) and lowered among those aged ≤20 years (13.56%). For gender, a high nominal positivity rate was detected in females (36.07%) than in males (28.37%). Association between the degree of severity of the infection and demographic risk factors recorded that mild infection (75%) was increased among individuals of ≤20 years, while moderate and severe infections were elevated significantly in groups of 21-40 and 41-60 years. The highly severe infections appeared in those aged 21-40 years (15.91%). Regarding gender, mild and moderate infections were elevated significantly in males; whereas severe and highly severe infections were increased significantly in females. In conclusion, this study is the first random epidemiological study investigating the prevalence of human brucellosis in rural areas in Iraq. Undifferentiated species of Brucella were detected in PCR-positive results. The incorporation of molecular techniques for the diagnosis will help resolve the Brucella genus and detection the primary sources that play roles in the transmission of infection.

Keywords: Demographic risk factor; Enzyme-linked immunosorbent assay (ELISA); Polymerase chain reaction (PCR); Brucella abortus; Brucella melitensis.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Figure 1
Figure 1
Level of severity of infection among seropositive study individuals Significant differences were expressed as * (P≤0.013), ** (P≤0.029), *** (0.036), **** (P≤0.043), ***** (P≤0.048)
Figure 2
Figure 2
Values of seropositive samples distributed among the levels of infection’s severity
Figure 3
Figure 3
Total positive results for testing 83 seropositive samples by molecular PCR assay
Figure 4
Figure 4
Distribution of 25 positive PCR samples based on the species of Brucella
Figure 5
Figure 5
PCR analysis by electrophoresis using 1.5% agarose gel stained with Ethidium bromide at 80 Volt and 100 Am for 1.5 hours, targeting BCSP31 gene of Brucella spp. Lane (M) represents the ladder marker (100-1500bp). Lane (NC) represents negative control. Lane (PC) represents positive control. Lanes (1, 2, 5, 10, 12, and 19 of 1st image; and 1, 2, 3, 4, 7, 13, 14, 17, 18, 19, 20, 21, 22, and 23 of 2nd image) represent negative samples for human brucellosis. Lanes (3, 4, 6, 7, 8, 9, 11, 13, 14, 15, 16, 17, 18, 20 and 21 of 1st image; and 5, 6, 8, 9, 10, 11, 12, 15 and 16 of 2nd image) represent positive samples for human brucellosis (Brucella spp.) at 223bp
Figure 6
Figure 6
PCR analysis by electrophoresis using 1.5% agarose gel stained with Ethidium bromide at 80 Volt and 100 Am for 1.5 hours, targeting the IS711 gene of B. abortus. Lane (M) represents the ladder marker (100-1500bp). Lanes (1-7) represent positive samples for human brucellosis (B. abortus) at 498 bp
Figure 7
Figure 7
PCR analysis by electrophoresis using 1.5% agarose gel stained with Ethidium bromide at 80 Volt and 100 Am for 1.5 hours, targeting the IS711 gene of B.melitensis. Lane (M) represents the ladder marker (100-1500bp). Lane (NC) represents negative control. Lane (PC) represents positive control. Lanes (1, 2, 3, 5, 6, 7, 8, 11, 12, 13, and 15) represent positive samples for human brucellosis (B. melitensis) at 731bp. Lanes (4 and 14) consider a representative image for other differentiated human Brucella species. Lane (9) considers a representative image for the negative samples of human brucellosis
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