Ringworm in calves: Risk factors, improved molecular diagnosis, and efficacy of Aloe vera gel extract for treatment

Abstract

Background: Calves dermatophytosis is a major public and veterinary health problem worldwide due to its zoonotic potential and economic losses in cattle farms. However, it has lacked adequate attention; thereby for effective control measures it is worth determining ringworm prevalence, risk factors and direct sample nested-PCR diagnostic indices as compared to conventional methods for dermatophytes identification. Moreover, Aloe vera gel extract (AGE) phenolic composition and its in-vitro and in-vivo anti-dermatophytic activity in comparison to antifungal drugs were evaluated. Results: Of 760 examined calves, 55.79 % showed ringworm lesions. 84.91% were positive for fungal elements in direct microscopy, and 79.72% were culture positive. Trichophyton verrucosum was the most frequently identified dermatophytes (90.24%). Risk of dermatophytosis is high in 4-6 month than 1-month aged calves (60% versus 41%), in summer and winter compared to spring and autumn seasons (66% and 54% versus 48%). Poor hygienic conditions, intensive breeding system, animals raised for meat production, parasitic infestation, crossbreed, and newly purchased animals were statistically significant risk factors correlated with dermatophytosis. One-step PCR targeting conserved regions in the 18S and 28S genes achieved unequivocal identification of T. verrucosum and T. mentagrophytes in hair samples. Nested-PCR achieved an excellent performance in all tested diagnostic indices and increased the species-specific detection of dermatophytes by 20 % as compared to culture. Terbinafine and miconazole were the most active antifungal agents for dermatophytes. Gallic acid, caffeic acid, chlorogenic acid, cinnamic acid, aloe-Emodin, quercetin, and rutin are the major phenolic compounds of AGE identified by High-performance liquid chromatography (HPLC). These compounds increased and synergized the anti-dermatophytic activity of AGE. The treated groups showed significantly lower clinical scores than the control group ( P < 0.05). The calves were successfully treated with topical AGE (500 ppm) resulting in clinical and mycological cure within 14-28 day of the experiment. Conclusions: Implementation of nested-PCR assay providing a rapid diagnostic tool for dermatophytosis augments and complement the conventional methods for initiating targeted treatments of calves ringworm. The recognized anti-dermatophytic potential of AGE is advantageous countenance to commercial drugs to go used in therapeutics.