Sarcoptic mange in wombats

Abstract

Sarcoptic mange, commonly referred to as scabies, is a cosmopolitan disease affecting seven different orders within the class Mammalia. It is caused by the mite Sarcoptes scabiei (Linnaeus, 1758) Latreille, 1802 which is an obligate parasite of the skin. The mite is typically oval shaped, dorsally rounded and ventrally flattened. Its length varies between 200 and 500 μm depending on its life-cycle stage. Of the Australian marsupials, only wombats and the koala (Phascolarctos cinereus) (Vombatiformes) and the common ringtail possum (Pseudocheirus peregrinus) (Pseudocheiridae) have been reported with sarcoptic mange. In wombats, sarcoptic mange has been reported as the major infectious disease affecting the group, although it mainly occurs in only one of the three species, the common wombat (Vombatus ursinus). In this species sarcoptic mange can be debilitating. Several reports of severe sarcoptic mange in common wombats describe animals as emaciated and lacking hair with a thick dry crust, composed of keratin, many mites and their debris, bacteria and neutrophilic debris adherent to the skin (Figure 1). This crust is similar to that found in domestic animals with hyperkeratotic sarcoptic mange and humans with Norwegian scabies. The thick crust may be fissured by the movement of the wombat (Figure 2). The underlying skin may also crack resulting in haemorrhage, pyoderma and sometimes cutaneous myiasis. This may encompass the entire body with the head, neck, shoulders and limbs more commonly affected. Typically, the epidermis is thickened and there is a mild predominantly mononuclear inflammatory infiltrate in the dermis. In some animals hypersensitivity reactions occur towards Sarcoptes, with few mites present in the skin. Intense pruritus, a characteristic sign of hypersensitivity reactions to Sarcoptes in humans and animals has been reported in wombats with sarcoptic mange. Only occasional outbreaks of sarcoptic mange have been recorded in the southern hairy-nosed wombat (Lasiorhinus latifrons) and the disease has not been reported in the northern hairy-nosed wombat (Lasiorhinus krefftii).