Filarial worms: a systematic review and meta-analysis of diversity in animals from Iran with emphasis on human cases

Abstract

Current systematic review and meta-analysis demonstrate the prevalence reports of filariasis in animals in Iran along with human cases. Studies were screened, relevant papers were selected and the random-effect model was used by forest plot with 95% confidence interval (CI). Of 17 records of human case-reports, particularly from Khuzestan province (5 cases), Dirofilaria repens was the most detected parasite (10 cases) with higher involvement of the right eye (7 cases) than other organs. Eleven animal species were reported to be parasitised by filarioids in Iran. The prevalence of Dirofilaria immitis in canids was 14.69% (95% CI: 10.33-19.67), with highest rates (20.92%; 95% CI: 13.84-29.03) in free-ranging dogs. Male (10.07%; 95% CI: 5.10-16.47) and more than 1-year old (20.77%; 95% CI: 8.66-36.42) dogs were more likely to be found infected. The frequency of other filarioids of zoonotic interest was: Acanthocheilonema reconditum in dogs 2.15% (95% CI: 0.71-4.33), Dipetalonema evansi in camels 10.16% (95% CI: 4.73-17.34), Onchocerca cervicalis in horses 3.63% (95% CI: 1.44-6.75%) and Onchocerca fasciata 16.57% (95% CI: 10.12-24.24%) in camels. Still, our knowledge on parasitic filariae in Iran is limited and more investigation is needed in both human and animal populations.

Keywords: Diversity; Filarioids; Iran; meta-analysis; systematic review.

Fig. 1.

PRISMA flow diagram describing included/excluded studies up to 1 December 2019 (Moher et al., 2009)

Fig. 2.

Forest plot of the prevalence of D. immitis in canids of Iran up to 1 December 2019. A square is appointed to each individual study with a horizontal line as confidence intervals and the area of each square is proportional to the study's weight in the meta-analysis. Also, a diamond is assigned to the meta-analysed measure of effect. A vertical line representing no effect is also plotted. If the confidence intervals for individual studies overlap with this line, it demonstrates that at the given level of confidence their effect sizes do not differ from no effect for the individual study.

Fig. 3.

A bias assessment plot from Egger for the prevalence of D. immitis in canids of Iran up to 1 December 2019. In the absence of publication bias, it assumes that studies with high precision will be plotted near the average, and studies with low precision will be spread evenly on both sides of the average, creating a roughly funnel-shaped distribution. Deviation from this shape can indicate publication bias.