Equine leptospirosis: Experimental challenge of Leptospira interrogans serovar Bratislava fails to establish infection in naïve horses

BACKGROUND

Little information is available about experimental inoculation of leptospirosis in horses and the pathogenicity of Leptospira interrogans serovar Bratislava in this host.

OBJECTIVES

To determine the serological, clinical, pathological and haematological responses of horses to L. interrogans serovar Bratislava strain PigK151.

STUDY DESIGN

Randomised controlled in vivo experiment.

METHODS

Ten seronegative female foals were divided into 2 groups, control (n = 4) and challenged (n = 6). The challenged group received 1 × 10⁹ leptospires divided equally between topical ocular and intraperitoneal injections. Blood and urine samples were analysed. The temperature was recorded daily for the first 9 days, then weekly. Sera were tested by microscopic agglutination test (MAT). Automated complete blood count, differential and chemistry panel were performed. Histopathological analysis was performed on sections of liver, kidney, urinary bladder, uterine body and pineal gland. Sample culturing was performed from blood, urine, liver, kidney, reproductive tract and vitreous humour.

RESULTS

No pyrexia was noted. PCR and culture were negative from all samples. Differences between groups were found in CBC, differential counts and serum biochemistry panel (or profile), suggesting that leptospiral challenge triggered an inflammatory response. No evidence of leptospirosis was found from histopathological analysis. All challenged foals developed a humoral response. The MAT allowed the confirmation of the infecting serovar at a later stage, but it also revealed cross-reactive results that were further explained by genomic analysis.

MAIN LIMITATIONS

This experimental challenge had two main limitations: (a) the results might have varied if another strain from the same serovar had been used and (b) the use of another route of infection and a higher bacterial dose might have achieved colonisation.

CONCLUSIONS

Based on these findings, it may suggest that L. interrogans serovar Bratislava is neither pathogenic nor host-adapted serovar for horses, although these results might have varied if another strain from the same serovar had been used instead.

Histopathological Investigation of Skin and Hides Damage of Small and Large Ruminants due to Naturally Infested Ticks

Ticks are important ectoparasites which transmit many disease pathogen to animals; these are labelled tick borne diseases (TBD). Tick induced damage to skin and hides has not received attention. Skin and hides are important for the leather product industry, particularly in Pakistan. Due to economic importance and financial loss by ticks in leather industry, the present study was designed to investigate skin and hides damage due to ticks at microscopic level. Naturally tick infested tissue samples of hides and skin were collected from slaughter houses. Primary lesions at tick feeding sites showed epidermal edema with adjacent dermal edema. Histopathological examination revealed degeneration of epidermal layer down to the basal layer. Epidermal and sub dermal layers often displayed focal necrosis infiltrated with neutrophils and mononuclear cells at tick bite sites. Hyperplasia of keratinocytes was also seen at sites of ruptured epidermis. Quality of leather depends upon the grain (Outer) surface skin/hides. Ticks infestation damages the outer surface, due to bites, inflammatory responses, and secondary bacterial infections that often become established at feeding sites. Control of ticks should be given consideration to reduce infestation induced losses in the leather industry in Pakistan.