The Mara Mobile Veterinary Unit
Field Report - July 2009
After immobilization the wire was cut off using a wire cutter and the resulting wound was treated using hydrogen peroxide and a tincture of iodine then sprayed with oxytetracycline spray. Long-acting oxytetracycline antibiotics and dexamethasone were also administered intramuscularly to take care of bacterial infection and the ensuing inflammation.
Revival of anaesthesia
After treatment, the animal was revived from anaesthesia using 48mgs of diprenorphine hydrochloride combined with 10mgs of atipamezole hydrochloride administered through the jugular vein, it rose up after 2 minutes and took off to the wild. It had a good prognosis after the removal of the wire and treatment of the wound.
Investigation of cases of mange infestation in wildlife of Mara
Investigations on the epidemiology of mange in cheetahs, Thompson gazelles and other wildlife in Mara was conducted during this month. It involved capture of cheetahs and Thompson’s gazelles with mange, treating and collection of skin scrapings for parasites identification and characterization.
One adult female gazelle was sighted in Mara Buffalo area of Koiyaki-Lemek conservancy, it had lesions suspected to be of mange infestation, it was then captured by darting using 2mgs of etorphine hydrochloride combined with 10mgs of xylazine hydrochloride, the drug took effect and it became recumbent after 6 minutes.
The lesions were closely examined and skin scrapping samples collected from the lesions on the hind thighs, perineum and lower abdomen. The animal was then treated using ivermectin (a broad spectrum anthihelmintic) administered subcutaneously. After treatment, it was revived from anaesthesia and released.
Pathogenesis and pathology of Mange
Sarcoptic scabie mite, the causative agent of mange in many animals, burrows into the skin to the level of stratum germinitivum using the cutting mouth parts, chelicerae, gnathosoma and cutting hooks on the legs. It is suspected that some parasites produce keratinases or proteolytic enzymes which aid in invasion and burrowing below the host's skin. Disruption and ingestion of cells and tissue fluids by the mites causes skin injuries and lesions. Mites secrete or excrete antigenic materials which elicit hypersensitivity reactions leading to inflammatory reactions, skin irritations and skin pathology.
Clinical signs of mange in Mara cheetahs
The course of the disease and clinical signs are determined by the immunological state of the host e.g. immunologically naïve, previously exposed, anergic or able to evoke hypersensitivity responses. Usually, initial signs include non-pruritic patches of erythematous papules progressing into saborrheic dermatitis, this progress to intense pruretic, extensive hyperkeratosis, marked alopecia (hair loss) & dermatitis.
End result is dysfunctional skin covering most parts of the body, greatly thickened, hairless, and grey coloured. (Mites are rarely seen in the advanced stages of the disease.) Listlessness, dehydration, anorexia, emaciation and death. In Mara, signs of mange in cheetahs are encrustating dermatitis with pruritis, thickened dry crusts on skin surface with fissures, marked alopecia, dehydration, emaciation and listlessness, death may occur if symptoms are severe.
Sarcoptic scabie are submacroscopic and not easy to diagnose. Diagnosis can be made in the field by observing the described clinical signs. Deep skin scrapings examined in 10% potassium hydroxide (KOH) is helpful in hosts with abundant parasites in skin. The parasite has idiosomal denticles and club-shaped setae used for identification. Enzyme-Linked Immunosorbent Assay (ELISA) test developed to confirm cases of lesions without mites or for serological surveys.
In stable populations, mange infestation is of less concern and has no long-term effect on population growth/survival. (Pence D. B et. al, 1983 and 1994).For endangered/threatened species (Cheetahs), capture and treatment is warranted. Avermectin group of drugs especially ivermectin has been used to treat domestic and wild species with much success. (Arends J. J et, al 1999). Ivermectin is the drug of choice for treatment of sarcoptic mange. Other treatments involve use of acaricides, antinflammatories, antibiotics and multivitamins.
Prevention and control
Prompt treatment and isolation of infected individuals. Identification and control of mites in preferred hosts that infect others, in cheetahs it is suspected that they acquire the parasite from Thompson's gazelles during hunting, but it is also possible that they can get it from other animals like impalas, wildebeests among others. Treatment and control of mange in domestic animals around wildlife areas is very important in the control of this disease in wildlife.
During this season of wildebeest migration from Serengeti to Mara, many cases of zebras with snares are being reported in Mara. Snaring and injuries of elands, common zebras and other animals in Naivasha are still a great threat to wildlife conservation in the area. The Central Rift veterinary unit through the support of Kenya Wildlife Service and the David Sheldrick Wildlife Trust (DSWT) continue to rescue as many animals as possible both in the Mara ecosystem and other parts of Central Rift region.
Report by: Dr. Domnic Mijele