Introduction

During November, the Central Rift Veterinary Unit attended to cases of wildlife disease and injuries in Naivasha and Masai Mara areas.  Most of the veterinary interventions carries out were successful as shown in the report.  The cases are those of lions, hippo and zebras, the other activity was the African swine fever disease surveillance in Ruma National park where the unit was involved in capture and samples collection from bush pigs for laboratory analysis, details of this are in the report.

Treatment of an adult male lion in Mara Triangle conservancy

The lion was reported to have serious injuries on the hind limb (gluteal muscles) that could have been caused by struggle during hunting.  The animal was then captured by chemical immobilization through darting using 350mgs of Ketamine hydrochloride combined with 350mgs of Xylazine hydrochloride.  It took about 6 minutes to become recumbent.  It had a deep wound on the medial side of the right hind limb near the inguinal region.  It was only a soft tissue injury not involving bones and cartilages.

The wound was then cleaned using clean water the debrided by hydrogen peroxide solution and tincture of iodine applied.  Intramuscular administration of antibiotics and antinflammatories was also instituted.  The wound was then sprayed using oxytetracycline antibiotic spray.  It was later on revived from anesthesia using 20mgs of Atipamezole administered intramuscularly.  The animal was put under close monitoring for the next few days and was reported to have good progress after treatment.

Postmortem examination of a juvenile male hippo in Keekorok river

This was a case of a juvenile hippo that died in a small water pool next to Keekorok lodge in Masai Mara.  The carcass was found floating in the pool, it was then pulled out using ropes and postmortem examination done.  It had numerous penetration wounds on the abdominal and thoracic regions, the carcass was already putrefied.  The wounds could have been inflicted by other hippos and the real cause of death could have been due to lung injuries.  Tissue samples were collected and preserved in absolute ethanol for DNA analysis.

Desnaring of Masai Giraffe in Crater Lake in Naivasha

This was a female adult giraffe that was found entangled by a wire round the shoulder and neck region, it was a loose wire that had not inflicted any traumatic injuries.  The animal was then restrained by chemical immobilization using 13mgs of etrophine hydrochloride combined with 20mgs of Xylazine hydrochloride by darting.  It went recumbent after about 5 minutes and the wire was cut off using a wire cutter, the animal was then revived from anesthesia and released feeling relieved.

Euthanasia of a common zebra with extensive traumatic injuries on the thoracic region

The case was found in Nderit farm in Naivasha, it was a case of an adult female zebra that had extensive wound on the shoulder that had been inflicted by a tight wire snare.  It had stayed in this condition for quite sometime but now it could hardly move due to pain and weakness.  The animal was captured by chemical immobilization, the wound was assessed and was found to have no chance of recovery.  It was later on euthanized in order to alleviate pain and suffering and the carcass disposed of in the thick bush.

Hoof trimming of a common zebra in KWS Annex sanctuary

The zebra had a hoof overgrowth on the left hind limb that really interfered with its movement, we encountered this while searching for a snared zebra within that sanctuary.  It was captured by darting and the hoof trimmed using a hacksaw then revived from anesthesia.

AFRICAN SWINE FEVER DISEASE SURVEILLANCE IN RUMA NATIONAL PARK

Introduction

Kenya Wildlife Service (KWS) veterinary department in collaboration with International Livestock Research Institute (ILRI) initiated African swine fever (ASF) disease surveillance in Ruma National park during the month of November, 2007.  The work that went on for more than one week involved capture and samples collection from bush pigs within the park.

Highlights about ASF

African swine fever (ASF) is a highly contagious disease of pigs, first described in Kenya by Montgomery (1921).  It is caused by a large DNA virus and is considered to be one of the most complex viral diseases to affect domestic animals.  The disease is endemic in many African countries south of the Sahara desert.  In Europe it is still endemic in Sardinia (Italy) and outbreaks were confirmed in the Alentejo region of Portugal in November 1999 (OIE) and inflicts significant socio-economic impact on affected countries.

Resevoir hosts and transmission of (ASF)

The ASF virus affects both wild and domesticated pigs and is transmitted by soft ticks of family Aragasidae, genus Ornithodoros.  In Africa, it is mainly transmitted through Ornithodoros moubata in Africa (Plowright et al., 1970) and Ornithodoros erraticus in the Iberian Peninsula (Sanchez Botija, 1963).

Ornithodoros corinaceus, a tick indigenous to the USA, has also been found to harbour and transmit ASF virus in experimental settings (Groocock et al., 1980), as has Ornithodoros savignyi which is present in Africa (Mellor and Wilkinson, 1985).

In Africa, ASF virus usually induces a non-apparent infection in three wild boar species: warthog (Phacochoerus aethipicus), giant forest hog (Hylochoerus meinerzhageni) and bush pig (Potamochoerus porcus).  Infection is characterized by levels of virus in the tissues and low or undetectable levels of viremia.  In the case of bush pigs P. porcus, viremia has been observed between 35 and 91 days following infection and the virus can persist in lymphatic tissues for 34 weeks (Anderson et al., 1998).  Viral infection normally moves from these animals to domestic pigs through a biological vector, Ornithodorous moubata, and not by direct transmission.

ASF virus infections in the African vector Ornithodoros moubata are transmitted by transovarial and transtadial routes, whilst only transtadial transmission has been observed in the European vector Ornithodoros erraticus.

Significane and objectives of ASF surveillance

African swine fever (ASF) is classified on OIE list A, which by definition contains only diseases that have the potential for very serious and rapid spread, producing serious socio-economic consequences (OIE, 1999).  The last five years (1985-1990) of the ASF Spanish eradication programme cost approximately US$92 million.

Communities living around Ruma National park do keep pigs which are slaughtered occasionally for food especially during festivities.  African swine fever is a disease of pigs but can induce a non apparent infection in wild pigs such as bush pigs which then act as reservoir hosts for the disease and may transmit the virus to the domestic pigs.

The main objectives of ASF surveillance is to confirm if the bush pig population within the park have ever suffered from the disease by conducting serological tests to detect ASF antibodies in serum.

To test some of the diagnostic kits that have been developed for diagnosis of ASF in both domestic and wild pigs.

If the virus is found to be circulating in Ruma bush pigs then control measures can be put in place to avoid transmission of the disease to domestic pigs that can lead to an outbreak and serious economic losses due to pig mortalities in Kenya.

Methodology for bush pig capture and samples collection

Bush pigs are nocturnal animals that can only be seen late in the night, they are also extremely shy and cannot come close to humans.  During day time they hide in deep thickets where they cannot be seen.  These factors make it difficult to capture and handle bush pigs for sero-surveillance.  In Ruma National park, they are commonly sighted near garbage collection sites within the residential areas at the park headquarters, Nyatoto gate, and Wiga gate. Apart from being in these areas, they are always seen at night while invading crop farms at night away from the park then hide in the nearby forest during day time.

Capture method

The use of nets for capture was the most reliable method and in Ruma, the capture team managed to capture one adult female bush pig at night.  The animal was found grazing in an open space within the compound, then the escape routes were sealed by the net and when the animal tried to get into the bush it got entangled onto the net.  It was then physically restrained by hands and net.  It was about 60kgs heavy with enlarged abdomen, suspected to be pregnant.

Samples collection

Blood samples were collected using a 19 gauge needle and a syringe from the femoral vein and coccygeal vein then drawn into 14ml plain tubes coated with clot retractor and EDTA coated tubes and put in a cool box overnight.  Ticks were picked from the skin of the animal using rat-toothed forceps and placed in small containers and placed in a cool place.  Tissue samples were also collected by cutting a small portion of the ear-pinnae.  Hair samples also plucked out from the roots.

Samples storage and processing

The blood samples were centrifuged at 1500 rounds per minute for 10  minutes then serum extracted into cryovials and kept in a deep freezer for submission to the lab for analysis.  Tick samples were also kept in a deep freezer, tissue samples were dissolved and kept in a freezer too.

Prevention and Control of (ASF)

Control of the disease is usually achieved by the control of tick vectors.  No treatment or vaccine is available for ASF and control of this disease is based on rapid laboratory diagnosis and the enforcement of strict sanitary measures.

Depending on the epidemiological status of the disease in a particular region, different measures are recommended.  In endemic areas of Africa, the most important factor is to control the natural tick vectors and wild pig reservoirs, and/or limit their contact with domestic pigs.  The identification and slaughter of sick and carrier animals is crucial to the control of the disease.

Conclusions/Recommendations

The work was concluded after the animals disappeared and were difficult to locate, the intention was to capture more than 10 bush pigs but due to low numbers of bush pigs in the park and their unpredictable movement patterns and difficulties of capturing at night, the team managed to capture and collect samples from only one bush pig.  The recommendations for the future work were:

• Put on collars to any bush pig captured for ease of tracking and location for continuous monitoring and samples collection over a period of time.
• The duration of biological samples collection for this project can be staggered over a longer period of time probably one year because it is only possible to capture 2 or 3 at a given time then they disappear.
• Opportunistically capture bush pigs whenever vet team goes to Ruma to attend to other cases and collect the required samples.
• Use of baited traps well designed for capture of bush pigs.

The veterinary team left Ruma and went to Masai Mara to treat a lion that was reported to have eye infection and a cheetah with skin disease.  Once again it was a successful month for the vet unit as all the cases reported were attended to promptly and effectively without any hitch.

Report by: Dr. Dominic Mijele