Sarcoptic mange is most fatal and contagious parasitic infestation of rabbits caused by scavenging mite, Sarcoptesscabiei of family Sarcoptidae, manifested by hyperkeratosis, alopecia, seborrhoea and severe pruritis. It is one of the most common diseases seen in rabbits leading to huge economical losses to the rabbit breeders¹. The lesions are usually dry crusty areas observed on ears, nose, feet and perineal region², ³. Poor hygiene and overcrowding are the two most critical predisposing factors for scabies⁴. This ectoparasite, also known as an itch mite, burrows into the epidermis of the skin and causes scabies in humans and mange in animals⁵.

Staphylococcosis is bacterial disease caused by Staphylococcus aureus in rabbitries, which are characterised by pododermatitis, mastitis, subcutaneous abscesses and septicaemia⁶. Occasionally, abscesses are also observedin lungs, liver and uterus, which may lead to infertility, poor production and even death⁷. Sarcoptes scabiei may invade skin barriers and excrete certain molecules, which inhibit innate immunity of host promoting the infections caused by Staphylococcus aureus and Streptococcus pyogenes⁶.

A carcass of a New Zealand white male adult rabbit brought to Department of Veterinary Pathology, GADVASU Ludhiana with the history of emaciation, lethargy and multiple skin lesions for necropsy examination. A thorough external examination of the carcasswas performed for the presence of ectoparasites or injury. The systematic necropsy examinationwas performed and gross lesions were recorded. Tissue samples were collected in 10% formalin, processed, sectioned and stained with haematoxylin and eosin stain as per the standard protocols⁸. Skin scrapings were collected from affected areas, were placed in a petridish, and treated with 10% KOH (Potassium hydroxide) solution. The mixture was stirred, centrifuged and supernatant discarded. A few drops of fluid on a slide were used to examine the mites under a microscope.

Samples from the skin lesions collected in sterile swab for bacterial isolation and were inoculated on nutrient agar and incubated at 37^OC for 24 hrs. The colonies were picked up for gram's staining. Cytosmear were Cultural growth employed to MALDI TOF (Matrix-Assisted Laser Desorption/Ionization-Time of Flight) for further confirmation.

Gross examination of the carcass revealed crusted irregular raised dried scabs in ears, pododermatitis and subcutaneous abscesses throughout the carcass (Figs. 1 and 2). Rounding of the heart was observed. There was catarrhal exudate in the stomach and intestine. Stomach mucosa also revealed congestion and few types of erosion.

Adult Sarcoptes scabiei parasites were detected in rabbit skin scrapings (Fig. 3). The adult mite have four pairs of short legs with oval, ventrally flattened and dorsally convex tortoise-like bodies and cuticular spines on the dorsal side. Adult female mite was having rounded body, shorter legs and anterior end with suckers (Fig. 4).

Histological examination of the skin lesions revealed diffuse irregular thickening of epidermis, hyperplasia of stratum spinosum along withformation of rete ridges and infiltration of mononuclear cells and cellular debris were seen in the epidermis. Parakeratotic hyperkeratosis of stratum corneum with serocellular crust formation was also evident (Fig. 5). Multiple cross sections of oval to irregular embedded mite were observed in stratum corneum, which was recognised by a chitinous cuticle, striated muscle and body cavity (Fig. 6). Lungs showed congestion, haemorrhages and bullae formation. Intestinal villi were sloughed off at places (Fig. 7). Glomerular blood vessels were congested and renal tubules were having pale eosinophilic proteinous mass. Liver revealed sinusoidal congestion and mild infiltration of mononuclear cells in periportal areas. Degeneration of hepatocytes was also evident.

On gram staining, gram-positive cocciwere observed which were present in singles, clusters and chains, resembling Staphylococcus spp. (Fig. 8). Bacterial culture of Staphylococcus aureus was confirmed by using MALDI TOF.

Ear mite and mange infestations have been described as severe skin conditions in both young and adult rabbits. The presence or lack of pruritis, the shape of the mite, and the distribution of lesions characterise S. scabiei mange in rabbits⁹. The presence of mites under a microscope, as well as distinctive skin lesions in various body areas, confirms the presence of sarcoptic mange in rabbits. Burrowing activity and mechanical damage induced by the parasites during excavation, irritating action of their secretion, allergic reactions to some of their extracellular products, and specifically release of interleukin-I leads to pathological lesions¹⁰.

On the basis of gross, histopathology, parasitology and microbiological findings, it was confirmed to be concurrent infection of sarcoptes mange and staphylococcus aureus in rabbit. Since it is highly contagious, steps should be taken to prevent it and otherwise may leads to heavy economic losses to rabbitry farms.

References