Infective larvae were harvested from a culture of eggs collected from adult Strongylus asini recovered from
a free-ranging Burchell's zebra, Equus burchelli, in the Kruger National Park. Worm-free zebra, horse and donkey foals were successfully infested, but infestation failed in a mule foal. At slaughter, 117-125 days post-infestation, S. asini in their 4th moult were recovered from the liver and portal veins. This is the first report of successful experimental infestation of these hosts with S. asini.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. 
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

De Vos, Valerius

Malan, F.S.

Pletcher, J.M.

Reinecke, R.K.

The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. 
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.Infective larvae were harvested from a culture of eggs collected from adult Strongylus asini recovered from
a free-ranging Burchell's zebra, Equus burchelli, in the Kruger National Park. Worm-free zebra, horse and donkey foals were successfully infested, but infestation failed in a mule foal. At slaughter, 117-125 days post-infestation, S. asini in their 4th moult were recovered from the liver and portal veins. This is the first report of successful experimental infestation of these hosts with S. asini

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Onderstepoort J. vet. Res .. 151-153 (1982) STUDIES ON STRONGYLUS ASINI. I. EXPERIMENTAL INFESTATION OF EQUINES F. S. MALAN°>, V. DE VOS(2), R. K. REINECKE<3> and J. M. PLETCHER<4> ABSTRACf MALAN, F. S., DEVOS, V., REINECKE, R. K. & PLETCHER, J. M. 1982. Studies on Strongylus asini. I. Experimental infestation of equines. Onderstepoort Journal of Veterinary Research, 49, 151-154 (1982). Infective larvae were harvested from a culture of eggs collected from adult Strongylus asini recovered from a free-ranging Burchell's zebra, Equus burchelli, in the Kruger National Park. Worm-free zebra, horse and donkey foals were successfully infested, but infestation failed in a mule foal. At slaughter, 117-125 days post-infestation, S. asini in their 4th moult were recovered from the liver and portal veins. This is the first report of successful experimental infestation of these hosts with S. asini. lNTRODUCfiON A donkey and a mule foal were bought when they Fully mature Strongylus asini were recovered by Jas- were about 1 month old and reared on a concrete floor at koski & Colglazier (1956) from cysts in the liver of a the farm. At the time of infestation they were about 3 Grevyi zebra, Equus grevyi that had died in the Chicago months old. Zoo USA. These worms were the cause of extensive All the animals were kept in pens with concrete floors . liver damage and peritonitis which was responsible for The animals were fed worm-free hay ad libitum and a the zebra's death. In this paper we report on the recovery pellet concentrate 3 times a day. Clean fresh water was of S. asini (Fig. 1) from free ranging Burchell's zebra, always available. Equus burchelli, in the Kruger National Park in the Re- All 4 trial animals were dosed with Albendazole*** at public of South Africa. 50 mg/kg with a stomach tube twice a day for 2 days. McCully • Kruger • Basson, Ebedes & Van Niekerk The mass of each animal at the time of infestation was: ( 1969) state that the extensive liver pathology and other lesions in the Burchell's zebra, both in the Kruger Natio- Zebra 130 kg nal Park and Etosha Park in South West Africa!Namibia, Horse 150 kg were due to Strongylus vulgaris. In the present report we Mule 55 kg will show that the cause of these liver lesions in the Donkey 55 kg Kruger National Park was S . asini and compare the host susceptibility of various equines to S. asini. MATERIALS AND METHODS Infective larvae Female S. asini were collected from the caecum and ventral colon of 2 zebras slaughtered during a parasite survey in the Kruger National Park in Aprill981. Addi-tional S. asini were collected from 2 zebras slaughtered in May 1981. The worms were placed in normal saline in a Petri dish and stored overnight in an incubator at 28 °C. A large number of eggs were laid. After 24 hours the worms were cut into small pieces and placed in a tea sieve. Saline was poured over these worm pieces while they were being lightly ground with a glass rod, and the eggs were washed through the sieve. All the eggs collected were mixed with horse faeces which had been obtained from a worm-free horse, i.e. an. animal that had repeatedly been dewormed beforehand. Vermiculite was added to the dung for aeration and cul-tures were made in 1 e wide-mouthed glass jars, which were then incubated at 28 oc. The infective larvae were harvested 11 and 12 days later, concentrated in a measuring cylinder and stored at 4 oc in a refrigerator. Experimental animals A young zebra stallion approximately 6 months old was darted with a combination of M99* and Aupyri-dol** and transported to the Hoechst Research Farm at Male lane. A horse filly about 1 year old was purchased at Caro-lina, Transvaal, and transported to the farm. 01 Hoechst Research Farm, P.O. Box 124, 1320 Malelane c21 Kruger National Park, Private Bag X402, 1350 Skukuza (JJ Faculty of Veterinary Science, P.O. Box 12580, OliO Onderste-poort <4! Section of Pathology, Veterinary Research Institute, P.O. Box 12502, OliO Onderstepoort * Reckitt and Coleman Pharmaceuticals (Pty) Ltd ** Janssen Pharmaceutica Received 21 April 1982- Editor 151 Infective larvae of S. asini were dosed by means of a stomach tube and 300 larvae were given to each animal on 21 May 1981 (Day 0) and a further 1 500 larvae to each animal6 days later on 27 May 1981 (Day +6). All the foals were killed from 21-23 September 1981. The age of the worms in days at slaughter in the different hosts was: Zebra Horse Mule Donkey 117 and 123, 118 and 124, 119 and 125, 119 and 125. Post-mortem technique The autopsies were conducted according to the tech-niques described by Malan, Reinecke & Scialdo (1981 a, b). In addition, special attention was given to the follow-ing: (a) The portal venous system was extensively opened for observing the lesions and recovery of all the worms. (b) The peritoneum, abdominal muscular layers, mesen-tery and kidney fat were dissected and examined for worms. (c) The lungs were cut into small pieces and placed in a 2f wide-mouthed jar containing normal saline, and the jar incubated in a water-bath at 40 °C for 4 hours . Any worms that might have migrated from the lungs into the saline solution were recovered by washing the contents on a sieve with apertures of 150 p.m. The helminths recovered were left in saline for 12 h and then killed in glycerine-alcohol mixture heated to 60 °C. The worms were stored in plastic specimen jars in the glycerine-alcohol mixture (60% absolute alcohol, 5% glycerine, 35% H20). REsULTS Zebra The general condition of the zebra was poor, with little subcutaneous, mesenteric or perirenal fat. *** Smith Kline STUDIES ON STRONGYLUS ASIN/. I. EXPERIMENTAL INFESTATION OF EQUINES Liver: Numerous nodules measuring 2-3 em in diam-eter could be seen elevating the capsular surface (Fig. 2). More nodules could be palpated deeper in the paren-chy~a. They were oval to round and were quite hard. Cuttmg through the nodules revealed in each a hard fiJ;>rous caps~l~ surroun~ing a cystic cavity which con-tamed S. astm and a thick red-brown fluid. Most con-tained a single worm, but some were larger and multi-locular and contained up to 4 worms. The nodules were associated with the portal blood supply to the liver. When opening the portal vein at the portal fissure and following the vein and its branches into the liver substance, numerous nodules containing 1 or more helminths were seen protruding into the lumens of the branches of the portal vein. A large thrombus, roughly 14 em long and having a diameter of 15 mm, was found in the portal vein. The periportal and hepatic lymph nodes were mark-edly enlarged. A . mesenterica cranialis: No worms or lesions were found. Lungs: A caseous nodule was found in the lung tissue, but no worms were found. Ascites: Four hundred me of a straw-coloured fluid was measured. Hydropericardium: Forty-five me of the same coloured fluid was present. Horse The carcass was in a healthy condition. Liver: No macroscopic changes were seen in the initial examination in situ of the liver. One nodule was identi-fied by palpation, but when the portal vein was opened at the portal fissure, 15 large (2 X 2 em) nodules were observed (Fig. 3). In addition, 2 thrombi were found in the intrahepatic branches of the portal vein. An additional 30 worms were recovered from nodules adjacent to the distal branches of the portal vein. A. mesenterica cranialis: No lesions or worms were seen. Ascites: Two hundred me of a straw-coloured fluid was measured. Hydropericardium: Eighteen me of straw-coloured fluid was measured. Mule No worms or lesions were seen. The mule was in very good condition. A. mesenterica cranialis: No worms or lesions were seen. Ascites: Two hundred and fifty me of fluid was reco-vered. Hydrothorax: Fourteen me of fluid was present. Donkey The general condition of this animal was very poor. Liver: The liver had the same external appearance as that of the zebra (Fig. 2), with numerous nodules throughout. The major difference was noted, however, when the portal vein was opened. Instead of numerous parasitic nodules, a severe thrombophlebitis was ob-served. Many S. asini were present in the thrombotic material which adhered to the roughened intimal surface of the vein (Fig. 3). The proximal intrahepatic branches of the portal vein were those most prominently involved. Numerous nodules were found in the smaller branches of the veins, the majority being associated with the right lobe of the liver. 152 A. mesenterica cranialis: No worms were recovered and no lesions were seen. Ascites: Fourteen me of a straw-coloured fluid was measured. Hydropericardium: Eighteen me of a straw-coloured fluid was measured. DISCUSSION Boulenger (1920), using specimens of S. asini sent to him from donkeys in Zanzibar and Nairobi, described S. asini as a large (18-42 mm long X 2,5 mm wide) strongyle, dark-red in colour, its head divided from the rest of the body, with a fairly large mouth (320 X 470 J.Lm) and a well-marked-off mouth collar. The dorsal gutter is well-developed and terminates behind the ante-rior margin. There is a single tooth at the base of the dorsal gutter which, like that of S. vulgaris, is divided into lateral projections which are much shorter than those of S. vulgaris (See the illustration of S. asini in Fig. 1). Nairobi, situated ± l 0 S and Skukuza in the Kruger National Park ± 25°S, being separated by about 2 600 km, represent different ecosystems. It is postulated that the normal hosts of S. asini should be sought among the wild zebra populations of Africa and that they as the true hosts possibly overflowed into domestic equines on com-munal grazing grounds, such as occurred in the donkeys in which Boulenger ( 1920) found the original specimens of S. asini. To test this theory 3 domestic equines (horse, donkey, mule) and a Burchell's zebra were artificially infested with infective larvae harvested from eggs of S. asini collected from zebras in the Kruger National Park. The donkey and zebra were the most susceptible species of the hosts tested and both of them showed debility and emaciation in the terminal phases of this study prior to slaughter for autopsy. The worm nodules in the Vena portae of the zebra were more prominent than those in the donkey, while more worms were found associated with the thrombo-phlebitis present in this vein in the donkey. This may indicate that part of the larval development occurs in the lumen of the V. portae in the donkey. If so, it is remi-niscent of the parasitic endarteritis produced by larval stages of S. vulgaris in equines. Neither the horse nor the mule exhibited obvious clini-cal signs, and, while the horse showed only a few nod-ules in the V. portae, the mule showed none at all. At slaughter 117-125 days post-infestation, S. asini in the 4th moult were recovered from the liver and portal vein of the zebra, donkey and horse, but none in the mule. We surmised that S. asini infestation is capable of caus-ing mortality in the zebra if the severe pathology in an experimental infestation is typical of a field case. The worms recovered were all in the 4th moult. The mean length of the females was 32, I mm, ranging from 25-38,5 mm. The mean length of the males was 29,9 mm, ranging from 22,5-34 mm. Theiler (1923) reports that the mean length of female S. vulgaris is 20 mm, while that of the male S. asini ranged from 18-32 mm and females from 30-42 mm. From these trials it seems that the parasitic life cycle can be summarized as follows: Mouth --+ gut --+ penetration --+ portal system --+ liver tissue --+ portal system --+ caecum and colon. The aim of the further trials will be to prove this postu-late. S. asini were never recovered from the A. mesente-rica cranialis or its branches and this is additional evi-dence that this is not a strain of S. vulgaris which nor-mally migrates to this artery and not to the V. portae. FIG. I Anterior end, lateral view of S. asini. Although the mouth capsule resembles that of S. vulgaris, the dorsal gutter is shorter and does not reach the anterior margin, and the teeth are much shorter than those of S. vulgaris FIG. 2 Liver of an experimentally-infested zebra in situ. Note the numerous nodules 2-3 em in diameter, elevating the surface of the capsule. At least I but as many as 4 S. asini were recovered from each nodule FIG. 3 The Vena portae of a horse experimentally infested with S. asini . Note thrombi in the lumen and nodules in wails of the portal vein FIG. 4 S. asini in the portal vein of an experimentally-infested donkey. Note the severe thrombophlebitis and the numerous S. asini in the lumen REFERENCES BOULENGER, C. L. , 1920. Sclerostomes of the donkey in Zanzibar and East Africa. Parasitology 12, 28-30. JASKOSKI, B. J . & COLGLAZIER, M. L., 1956. A report of Stron-gylus asini from the United States. Journal of the American Veteri-nary Medical Association, 129, 513-514. MALAN, F. S., REINECKE, R. K. & SCIALOO, ROSINA C. , 1981 a. Recovery of helminths post-mortem from equines. I. Parasites in arteries, subperitoneum, liver and lungs. Onderstepoort Journal of Veterinary Research, 48, 141-143. F. S. MALAN, V. DE VOS , R. K. REINECKE & J. M. PLETCHER 153 MALAN, F. S. , REINECKE, R. K. & SCIALOO •. ROSINAC. , ~981 b. Recovery of helminths post-mortem fr?m e9mnes. IT. Helrmn!hs and larvae of Gasterophilus in the gastro-mtestmal tract and oestnds from the sinuses. Onderstepoort Journal of Veterinary Research, 48, 145-147. McCULLY R. M., KRUGER, S. P., BASSON, P. A., EBEDES, H. & VAN NIEKERK, J. W., 1969. Strongylidoses: Delefondiasis in the zebra. Onderstepoort Journal of Veterinary Research, 36, 105-128. THEILER GERTRUD, 1923. The strongy1ids and other nematodes parasiti~ in the intestinal tract o~ South African equines. Annual Report of the Director of Vetennary Research, Umon of South Africa, 91!0, 601-773. 

Studies on Strongylus asini. I. Experimental infestation of equines

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Studies on Strongylus asini. I. Experimental infestation of equines

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