Parasites of domestic and wild animals in South Africa. XLI. Arthropod parasites of impalas,Aepyceros melampus,in the Kruger National Park

Ectoparasites were collected from impalas, Aepyceros melampus, at four localities within the Kruger National Park, namely Skukuza, in the Biyamiti region, Crocodile Bridge and Pafuri. Animals were also examined at Skukuza during a severe drought and at Skukuza and Pafuri towards the end of a second drought. Parasite burdens were analysed in relation to locality, sex, age class, month and drought. The impalas were infested with 13 ixodid ticks species, including two that were identified only to genus level. Except for four animals at Pafuri, all were infested with Amblyomma hebraeum. The highest intensity of infestation with larvae of this tick occurred from April to June and during November and December at Skukuza and in the Biyamiti region. Infestation with nymphs was highest during late winter. All animals were infested with Boophilus decoloratus, and the intensity of infestation was highest during spring. The intensity of infestation with Rhipicephalus appendiculatus was highest at Crocodile Bridge and at Pafuri, and that of Rhipicephalus zambeziensis at Skukuza. With both the latter species the intensity of infestation of larvae was highest from April to August, of nymphs from July to September or October and of adults during February and March. Rhipicephalus kochi was present only at Pafuri. The impalas also harboured five louse species and two species of hippoboscid flies. The intensity of infestation with lice tended to be greater during late winter and spring than during other seasons and greater on lambs than on yearlings on which it was greater than on adult animals.     

Anthelmintic efficacy in captive wild impala antelope (Aepyceros melampus) in Lusaka, Zambia

There has been an increase in the number of wild ungulates kept in captivity for ecotourism and conservation in Zambia and these animals are susceptible to a number of diseases including gastrointestinal helminth infections. Surveys to determine anthelmintic efficacy to gastrointestinal nematodes in captive-wildlife are not common and there have been no reports of anthelmintic resistance in captive-wildlife in Zambia. This study was carried out to determine the efficacy of the benzimidazole anthelmintic fenbendazole in captive wild impala (Aepyceros melampus) in Zambia. During the month of April 2011, at the end of the rainy season, the faecal egg count reduction test was performed at a private game facility for assessing anthelmintic efficacy of oral fenbendazole and the anthelmintic treatment showed an efficacy of 90%. Haemonchus spp. and Trichostrongylus spp. were the predominant genera present before treatment, but Haemonchus spp. larvae were the only genus recovered from the faecal cultures after anthelmintic treatment. This represents the first documentation of anthelmintic treatment failure in captive wild-antelopes in Zambia. It also demonstrated the ineffectiveness of the common traditional practice of deworming captive-wild antelopes at the end of the rainy season due to the rapid re-infection of impala that occurs due to high pasture infectivity. Suggestions on changes to current anthelmintic use/practices that will make them more efficacious and reduce the possibility of development of anthelmintic resistance in captive wild game in Zambia are also made.     

Chemical capture of impala (Aepyceros melampus): A review of factors contributing to morbidity and mortality

Objective

To review the factors that contribute to morbidity and mortality of impala undergoing chemical capture, and discuss how they are potentially mitigated.

Ixodid ticks of impala (Aepyceros melampus) in Swaziland: effect of age class,sex, body condition and management

Five species of ixodid ticks, Amhlyomma hebraeum, Boophilus decoloratus, Rhipicephalus appendiculatus, R. evertsi evertsi and R. muehlensi, were commonly collected from impala (Aepyceros melampus) in the Mlawula-Mbuluzi-Simunye Nature Reserve and Protected Area complex in north-eastern Swaziland. The prevalence and apparent intensity of infestation of most tick species was greater on yearlings (13-24 months of age) and adults (> 24 months) than on lambs (≤12 months), and on adult males than on adult females. The packed cell volume and marrow dry weight were lower in impala infested with A. hebraeum, and in lambs and adults with moderate to heavy loads of R. muehlensi and/or R. appendiculatus. The age and sex patterns of tick infestation were probably determined by both body condition and host behaviour. The prevalence and apparent intensity of infestation of most tick species was greater in the unmanaged, densely populated area of the reserve than in the managed area from which impala had been culled. This trend was consistent in all months, and in all age classes.     

Causes of mortality in impala (Aepyceros melampus) on 20 game farms in Zimbabwe

The most common cause of death in impala (Aepyceros melampus) herds on 20 game farms in Zimbabwe was stress or physical injury during capture. Acute fascioliasis due to Fasciola gigantica was identified as the main disease problem associated with smaller game farms and where impala had been recently introduced. Losses associated with ticks and tick-borne diseases were rare. Impala in Zimbabwe are maintained in a healthy condition on game farms where they are given supplementary feed during the dry winter.     

Linognathus vituli (Anoplura: Linognathidae): population growth,dispersal and development of humoral immune responses in nai;ve calves following induced infestations

Growth of Linognathus vituli populations following establishment at a point source was followed for 16 weeks on eight louse-na?ve Holstein calves. Dispersal of lice from the point of infestation (withers) was monitored by examination of known louse predilection sights. Mean louse indices increased during the initial weeks reaching maximum mean values at 8 weeks post-infestation (p.i.). Subsequently, mean indices decreased, reaching a plateau that persisted through weeks 14 and 15 p.i. There was little movement away from the withers until 5 weeks p.i. Subsequently, numbers of lice on the withers declined, while increasing at sites on the head. A few lice were noted on the dewlap and topline sites. Host antibody responses to crude nymph antigens, measured by enzyme-linked immunosorbent assay (ELISA), were generally evident within 2-4 weeks of infestation. Examination of individual host data showed louse populations could be categorized relative to the mean population size for the group. Two animals were considered 'chronic', having louse populations that persisted throughout the study and whose louse indices were >150% of the group mean. Two animals were classified as 'resistant' having lice present for only a portion of the study and whose louse indices <40% of the group mean. The remaining animals had louse indices between 62 and 137% of the group mean. Antibody profiles of the individuals were not as clearly categorized, although the 'resistant' animals were only positive for short periods of time, roughly corresponding to the time when lice were observed.     

Immobilisation of impala (Aepyceros melampus) with a ketamine hydrochloride/medetomidine hydrochloride combination, and reversal with atipamezole hydrochloride

A combination of medetomidine hydrochloride (medetomidine) and ketamine hydrochloride (ketamine) was evaluated in 16 boma-confined and 19 free-ranging impalas (Aepyceros melampus) to develop a non-opiate immobilisation protocol. In free-ranging impala a dose of 220 +/- 34 microg/kg medetomidine and 4.4 +/- 0.7 mg/kg ketamine combined with 7500 IU of hyaluronidase induced recumbency within 4.5 +/- 1.5 min, with good muscle relaxation, a stable heart rate and blood pH. PaCO2 was maintained within acceptable ranges. The animals were hypoxic with reduced oxygen saturation and low PaO2 in the presence of an elevated respiration rate, therefore methods for respiratory support are indicated. The depth of sedation was adequate for minor manipulations but additional anaesthesia is indicated for painful manipulations. Immobilisation was reversed by 467 +/- 108 microg/kg atipamezole hydrochloride (atipamezole) intramuscularly, but re-sedation was observed several hours later, possibly due to a low atipamezole:medetomidine ratio of 2:1. Therefore, this immobilisation and reversal protocol would subject impalas to possible predation or conspecific aggression following reversal if they were released into the wild. If the protocol is used on free-ranging impala, an atipamezole:medetomidine ratio of 5:1 should probably be used to prevent re-sedation.     

Eimeria capricornis n.sp., E. nihonis n.sp., E. naganoensis n.sp., and E. kamoshika n.sp. (Protozoa: Eimeriidae) from the Japanese serow, Capricornis crispus

Eimeria capricornis n.sp., E. nihonis n.sp., E. naganoensis n.sp. and E. kamoshika n.sp. were detected from the Japanese serow, Capricornis crispus. The oocysts of these species were ovoid to ellipsoid, measuring 48.02 +/- 0.53 x 33.93 +/- 0.35 microns, 29.73 +/- 0.45 x 21.01 +/- 0.29 microns, 20.04 +/- 0.05 x 15.77 +/- 0.04 microns and 30.02 +/- 4.24 x 14.58 +/- 2.03 micron, respectively. In all the species the micropyle was observed, but the micropylar cap and oocyst residuum were not present. The polar granules were observed in the oocysts of E. capricornis. The sporocysts of the above species were spherical to elongate ovoid, measuring 15-23 x 8-13 microns, 14-16 x 7-10 microns, 11-13 x 6-8 microns and 8-10 x 6-7 microns, and the sporulation time was 6, 3, 3 and 6 days, respectively. The sporocyst residuum and refractile body were seen in all the species. In the sporocysts of E. naganoensis and E. kamoshika tiny Stieda body was seen, but not in the other two species. These four Eimeria species were not infective to goats.     

Evaluation of the reliability of pulse oximetry,at different attachment sites,to detect hypoxaemia in immobilized impala (Aepyceros melampus)

ObjectiveEvaluation of the reliability of pulse oximetry at four different attachment sites compared to haemoglobin oxygen saturation measured by a co-oximeter and calculated by a blood gas analyser in immobilized impala.Study designRandomized crossover study.AnimalsA total of 16 female impala.MethodsImpala were immobilized with etorphine or thiafentanil alone, or etorphine in combination with a novel drug. Once immobilized, arterial blood samples were collected at 5 minute intervals for 30 minutes. Then oxygen was insufflated (5 L minute⁻¹) intranasally at 40 minutes and additional samples were collected. A blood gas analyser was used to measure the arterial partial pressure of oxygen and calculate the oxygen haemoglobin saturation (cSaO₂); a co-oximeter was used to measure the oxygen haemoglobin saturation (SaO₂) in arterial blood. Pulse oximeter probes were attached: under the tail, to the pinna (ear) and buccal mucosa (cheek) and inside the rectum. Pulse oximeter readings [peripheral oxygen haemoglobin saturation (SpO₂) and pulse quality] were recorded at each site and compared with SaO₂ and cSaO₂ using Bland-Altman and accuracy of the area root mean squares (A_rms) methods to determine the efficacy. P value < 0.05 was considered significant.ResultsPulse quality was ‘good’ at each attachment site. SpO₂ measured under the tail was accurate and precise but only when SaO₂ values were above 90% (bias = 3, precision = 3, A_rms = 4). The ear, cheek and rectal probes failed to give accurate or precise readings (ear: bias = −4, precision = 14, A_rms = 15; cheek: bias = 12, precision = 11, A_rms = 16; and rectum: bias = 5, precision = 12, A_rms = 13).Conclusions and clinical relevanceIn order to obtain accurate and precise pulse oximetry readings in immobilized impala, probes must be placed under the tail and SaO₂ must be above 90%. Since SaO₂ values are usually low in immobilized impala, pulse oximeter readings should be interpreted with caution.     

Comparison of cardiopulmonary effects of etorphine and thiafentanil administered as sole agents for immobilization of impala (Aepyceros melampus)

ObjectiveTo compare the cardiopulmonary effects of the opioids etorphine and thiafentanil for immobilization of impala.Study designTwo-way crossover, randomized study.AnimalsA group of eight adult female impala.MethodsImpala were given two treatments: 0.09 mg kg^–1 etorphine or 0.09 mg kg^–1 thiafentanil via remote dart injection. Time to recumbency, quality of immobilization and recovery were assessed. Respiratory rate, heart rate (HR), mean arterial blood pressure (MAP) and arterial blood gases were measured. A linear mixed model was used to analyse the effects of treatments, treatments over time and interactions of treatment and time (p < 0.05).ResultsTime to recumbency was significantly faster with thiafentanil (2.0 ± 0.8 minutes) than with etorphine (3.9 ± 1.6 minutes; p = 0.007). Both treatments produced bradypnoea, which was more severe at 5 minutes with thiafentanil (7 ± 4 breaths minute^–1) than with etorphine (13 ± 12 breaths minute^–1; p = 0.004). HR increased with both treatments but significantly decreased over time when etorphine (132 ± 17 to 82 ± 11 beats minute^–1) was compared with thiafentanil (113 ± 22 to 107 ± 36 beats minute^–1; p < 0.001). Both treatments caused hypertension which was more profound with thiafentanil (mean overall MAP = 140 ± 14 mmHg; p < 0.001). Hypoxaemia occurred with both treatments but was greater with thiafentanil [PaO₂ 37 ± 13 mmHg (4.9 kPa)] than with etorphine [45 ± 16 mmHg (6.0 kPa)] 5 minutes after recumbency (p < 0.001). After 30 minutes, PaO₂ increased to 59 ± 10 mmHg (7.9 kPa) with both treatments (p < 0.001).Conclusions and clinical relevanceThe shorter time to recumbency with thiafentanil may allow easier and faster retrieval in the field. However, thiafentanil caused greater hypertension, and ventilatory effects during the first 10 minutes, after administration.     

Observations on the life-cycles and larval morphogenesis of Haemonchus bedfordi,Impalaia tuberculoid and Longistrongylus sabie (Nematoda: Trichostrongyloidea) parasitic in impala,Aepyceros melampus

The previously unknown life-cycles of Haemonchus bedfordi, Impalala tuberculata and Longistrongylus sabie parasitic in impala, are recorded. Observations on the morphology of the developmental stages and their habitat of these three nematode species are described. The similarities and differences to closely related species or subspecies are discussed.The morphology of the developmental stages of Haemonchus bedfordi are compared to the Haemonchus spp., H. contortus and H. placei.     

Influence of lactation on the prolactin secreting cells of the hypophysis of impala (Aepyceros melampus): an immunocytochemical and computer image analysis study

Acute stress in the course of wildlife management has been intensively investigated. Chronic stress, on the contrary, has not been researched at all, probably due to the difficulty in measuring it as a result of the overriding effect of the physiological response to the restraining of wild animals. It was therefore decided to evaluate the use of immunocytochemistry, combined with computer image analysis to try and determine the magnitude of the structural changes of various hormone-secreting cells of the hypophysis. Since it was a pilot study to determine whether the combination of immunocytochemistry with computer image analysis could be of value to distinguish between two normally diverse groups, it was decided to compare the relative activity of prolactin secreting cells of lactating and non-lactating impala ewes. After transforming the prolactin immunoreactive area data by log10 to fall inside the parameters for kurtosis and skewness, a significant difference (P < 0.05, 5-% level, 2-tail) with the parametric t-test could be shown between the mean prolactin immunoreactive area of lactating (3.0751 micron 2) and non-lactating (3.0467 micron 2) ewes. However, the Pearson product moment (r = 0.03) showed that this difference may not be important for all practical reasons. This may be due to either sampling errors or limitations of computer image analysis, as it was often difficult to distinguish individual prolactin immunoreactive areas. Furthermore, a significant increase in the total prolactin immunoreactive areas of lactating ewes was also established. This technique, however, could distinguish between the hypophysis of lactating and non-lactating impala ewes, and with further refinement could be a useful tool in determining chronic stress in wildlife populations.     

Trichostrongylus auriculatus n. sp. (Nematoda: Trichostrongylidae) from the steenbok, Raphicerus campestris (Thunberg, 1811)

During a pilot survey of the parasites of some artiodactylids in the Kalahari Gemsbok National Park a new species of Trichostrongylus Looss, 1905 was recovered from the small intestine of a steenbok, Raphicerus campestris (Thunberg, 1811), a gemsbok, Oryx gazella (Linnaeus, 1758), and a red hartebeest, Alcelaphus buselaphus (Pallas, 1766). The male spicules were 0,120-0,148 mm long and an ear-shaped protuberance was present on the shaft of the left spicule. The presence of only a single protuberance is characteristic of the species.     

Entamoeba struthionis n.sp. (Sarcomastigophora: Endamoebidae) from ostriches (Struthio camelus)

In the present work we identify the species of Entamoeba from ostriches (Struthio camelus). The complete sequence of the small subunit ribosomal RNA gene from this organism has been compared with those published for other species of the genus and clear differences have been found. These results confirm previous data which showed differences on parasite morphology and class of host with the other Entamoeba species. Taking all these data together, it can be concluded that the organism from ostriches is a new species whose proposed name is Entamoeba struthionis n.sp. This species probably infects rheas (Rhea americana), but genetic analysis of isolates from this host should be performed to confirm morphological data. Also, comparison of gene sequences with data from other authors on cysts recovered from human stool samples showed the possibility that this amoeba may affect humans. Further studies are needed to determine the risk of transmission of this new species to humans.     

Cryptosporidium ryanae n. sp. (Apicomplexa: Cryptosporidiidae) in cattle (Bos taurus)

A new species, Cryptosporidium ryanae, is described from cattle. Oocysts of C. ryanae, previously identified as the Cryptosporidium deer-like genotype and recorded as such in GenBank (AY587166, EU203216, DQ182597, AY741309, and DQ871345), are similar to those of Cryptosporidium parvum and Cryptosporidium bovis but smaller. This genotype has been reported to be prevalent in cattle worldwide. Oocysts obtained from a calf for the present study are the smallest Cryptosporidium oocysts reported in mammals, measuring 2.94-4.41micromx2.94-3.68microm (mean=3.16micromx3.73microm) with a length/width shape index of 1.18 (n=40). The pre-patent period for two Cryptosporidium-na?ve calves fed C. ryanae oocysts was 11 days and the patent period was 15-17 days. Oocysts were not infectious for BALB/c mice or lambs. Fragments of the SSU-rDNA, HSP-70, and actin genes amplified by PCR were purified and PCR products were sequenced. Multi-locus analysis of the three unlinked loci demonstrated the new species to be distinct from all other species and also demonstrated a lack of recombination, providing further evidence of species status. Based on morphological, molecular and biological data, this geographically widespread parasite found only in Bos taurus calves is recognized as a new species and is named C. ryanae.