Effect of repeated oxfendazole treatments on small strongyle infections in Shetland ponies

Overwintering of horse cyathostomes as inhibited third stage larvae (L3) and the effect of repeated oxfendazole (OFZ) treatment on strongyle infections were studied in an experiment with two groups of three Shetland ponies. Both groups were grazed together from May 28 to November 11, 1986 and subsequently housed. Treatments with 10 mg OFZ kg-1 were given on May 26, July 1 and July 28 and again one week before each group was necropsied in December and April, respectively. Worm populations of both groups were dominated by inhibited early L3. The proportion of fourth stage larvae (L4) was significantly higher in April than in December. The faecal egg counts showed that the OFZ treatment in May was more effective than those in July. This resulted in high pasture larval counts from the end of August onwards. The final treatments revealed a low efficacy against L3 and L4 but not against adult worms.     

Epidemiological observations on Gasterophilus intestinalis and G. nasalis in donkeys from Morocco.

During a 24 month period, 198 donkeys were examined for Gasterophilus intestinalis and Gasterophilus nasalis larvae. Gasterophilus intestinalis was found in 97.5% and G. nasalis in 95.5% of donkeys. The third instars (L3) of both species occurred during all months of the year and so did the second instars (L2), except in April (G. nasalis) and May (G. intestinalis). Over 75% of the animals had up to 200 larvae and 1.5% had over 600 larvae. The maximum number of both L2 and L3 larvae found in any animal was 418 G. intestinalis, 433 G. nasalis and 715 of both species combined. The seasonal variation in the numbers and development status of larvae indicated that the period of greatest activity of adult flies of G. intestinalis was from August/September to November, and that of G. nasalis from May to September. Consequently, the L2 larvae in the stomachs were in peak numbers between November and January for G. intestinalis and between July and September for G. nasalis. The L3 larvae of G. intestinalis had peak numbers between December and July, and those of G. nasalis between October and March. During January-March, most of the L2 larvae of G. nasalis were trapped in polypous nodules near the pyloric end of the stomach. It is concluded that the high-risk period for infection is during late spring and autumn, leading to the heavy larval burden of Gasterophilus in the stomach of donkeys during winter.     

Inhibited development of trichostrongylids of sheep in northern Nigeria.

Worm counts from Yankassa ewes, lambs and tracer lambs grazing unimproved pasture at Zaria were obtained each month during the rainy season of 1976. In June and July up to 14 per cent of the Haemonchus contortus populations consisted of early fourth stage larvae (L4). In August this increased to more than 55 per cent and in October to more than 95 per cent. From June to August most of the abundant late L4 contained rodlike crystals. More than 95 per cent of the Haemonchus contortus populations of two lambs killed two weeks after infection with infective larvae, cultured for seven days at 25 degrees to 30 degrees C in the dark, were early L4. Inhibited 3rd stage Trichostrongylus spp did not exceed 26 per cent of the worm populations.     

Epidemiology of Fasciola hepatica infection in the Paraíba River Valley, S?o Paulo, Brasil

The study revealed that although Lymnaea columella and Stenophysa marmorata were found in the same habitat, only L. columella harbored intramolluscan stages of F. hepatica. The population density of L. columella cyclically decreased between September and February, and increased from March to September. The drought that occurred between June and November 1981 dramatically reduced the number of snails collected. Larger snails were collected in March-July and November-December, while the smaller snails were collected in January-February and August-October, suggesting that there may be two generations of L. columella per year. The highest prevalence levels of infection in L. columella were: first year, June 8.82%, September 9.09% and October 10.52%; second year, March 6.25% and April 6.89%; third year, July 7.69%, August 10.25%, April 17.91% and May 13.91%. Results obtained with tracer sheep showed that the largest numbers of metacercariae were on pasture between June and October, and between March and April, but the infection was present during most of the year.     

Efficacy of moxidectin against gastrointestinal nematodes of cattle.

Three groups of 11 naturally infected crossbred beef calves were injected subcutaneously with moxidectin 1 per cent injectable at 0.2 or 0.3 mg moxidectin/kg bodyweight or with the unmedicated vehicle. Nematode infections had been acquired during grazing from December to April. Based on the faecal egg counts and total worm counts of the control calves at necropsy (11 to 13 days after treatment) most of the calves had heavy parasitic burdens. Ostertagia ostertagi was predominant and the mean numbers of adults, developing fourth stage larvae (L4) and inhibited early L4 were 45,906, 10,061 and 68,918, respectively. Haemonchus placei and Trichostrongylus axei were also present in the abomasa. Three species of Cooperia, Oesophagostomum radiatum L4 and T colubriformis adults were found in the intestinal tract. Both dosages of moxidectin were equally effective (P < 0.05) against all the abomasal nematodes (99.9 to 100 per cent) and the intestinal tract nematodes (99.4 to 100 per cent). No adverse reactions to the moxidectin treatment were observed. Abomasal pathology characteristic of heavy O ostertagi infection was observed in the control calves, but not in the treated calves.     

Epidemiology and control of equine strongylosis at Newmarket

Seasonal rises in mean faecal egg output were observed in grazing ponies in spring (578 eggs per gram) and in summer (930 epg) on 30 April and 2 September, respectively, in untreated ponies. Pasture infectivity reached a peak of 18,486 third stage larvae (L3)/kg on 17 September, two weeks after peak egg counts, coincidental with abundant September rainfall (103.0 mm). Differentiation of infective larvae from pasture showed the cyathostomes (small strongyles) to be predominant, but Trichostrongylus axei assumed major importance from late August to October. The large strongyles were rarely detected: Strongylus vulgaris was found only once and S edentatus only twice. The most effective parasite prophylaxis was achieved by twice weekly removal of faeces. In this group, concentrations of infective L3 on pasture reached a maximum of 1000 L3/kg, compared to 18,486 L3/kg for a control group and 4850 to 10,210 L3/kg for anthelmintic treatment groups. The removal of faeces increased the grazing area by about 50 per cent, by eliminating the characteristic separation of horse pasture into roughs and lawns. Spring and summer anthelmintic treatments of mature ponies with oxibendazole were effective in reducing the late season rise in pasture infectivity to 4850 L3/kg, but treatment of young ponies (mainly yearlings) with ivermectin every eight weeks or oxibendazole every four weeks resulted in pasture infectivity as high as 10,000 L3/kg. There was evidence of cyathostome resistance to benzimidazole drugs.     

The seasonal prevalence of inhibited development of Haemonchus contortus in sheep in Senegal

Throughout a period of 13 months, the abomasa of 1024 sheep, living in a sahelian region, were examined for adult Haemonchus contortus and their inhibited L4 larvae. Of these 796 (78%) were found harbouring H. contortus, but with low worm burdens (geometric mean 37). Significant numbers of inhibited larvae appeared early in the dry season (November) and they represented 49% of the total in December. A similar proportion of inhibited larvae were present until April and after that their number declined abruptly. It was concluded that Haemonchus sp. survives the dry season as hypobiotic larvae as well as adults.     

The seasonal incidence of coccidia infections in trade cattle,sheep, and goats in Nigeria

Summary

A survey of coccidia infections in trade cattle, sheep, and goats was undertaken in Nigeria between April 1978 and March 1979.

Faecal examinations showed coccidia oocysts in 1,456 (56 per cent) of 2,600 calves, 832 (80 per cent) out of 1,040 sheep, and 468 (45 per cent) out of 1,040 goats. There were relatively few coccidia oocysts between October and March and peaks occurred in August and September. Nine species of Eimeria were identified in bovine faeces, and seven species in both sheep and goats.

Eimeria bovis and E. zurnii are predominant in cattle, whereas E. faurei and E. ninakohlyakimovae have the highest percentage occurrence in sheep and goats in Nigeria. The effects of seasonal influences on the abundance of coccidia oocysts among ruminants in Nigeria are stressed.     

Parasites of domestic and wild animals in South Africa. XLV. Helminths of dairy calves on dry-land Kikuyu grass pastures in the Eastern Cape Province

Successive pairs of approximately 4-month-old Friesland bull calves, raised under worm-free conditions, were exposed to helminth infection for 14 days on dry-land Kikuyu grass pastures at 28-day to monthly intervals, on a coastal farm in a non-seasonal rainfall region of the Eastern Cape Province. With the exception of one pair of calves exposed for 28 days, this procedure was repeated for 28 consecutive months from December 1982 to March 1985. The day after removal from the pastures one calf of each pair was slaughtered and processed for helminth recovery and the other 21 days later. Both members of the last four pairs of calves were killed 21 days after removal from the pastures. Sixteen nematode species were recovered from the calves, and infection with Ostertagia ostertagi was the most intense and prevalent, followed by Cooperia oncophora. The calves acquired the greatest number of nematodes from the pastures from June to October of the first year and from June to August of the second year of the survey. Few worms were recovered from the tracer calves examined from November or December to March or April in each year of the survey. The seasonal patterns of infection with Cooperia spp., Haemonchus placei, Nematodirus helvetianus, Oesophagostomum spp., O. ostertagi and Trichostrongylus axei were all similar and were negatively correlated to atmospheric temperature and evaporation. Slight to moderate arrest in the development of fourth stage larvae occurred from July to September in Cooperia spp., April to July in H. placei, and August to October in O. ostertagi and Trichostrongylus spp. during the first year of the survey. Too few worms were present in the second year to determine a seasonal pattern of arrest. Species survival during the hot and windy summer months appeared to be achieved via a combination of arrested larval development and an ageing residual population of adult worms in the host, and a small extant population of infective larvae on the pastures.     

季节对沼泽型水牛采卵效果和卵母细胞体外成熟的影响

利用屠宰场屠宰的沼泽型水牛卵巢采集卵母细胞,统计了一年中4个季度1—3、4—6、7—9、10—12月份每个卵巢平均获卵母细胞总数、可用卵母细胞数及不可用卵母细胞数。结果：每个卵巢平均获卵母细胞总数分别为4.06枚±0.63枚、4.62枚±0.75枚、4.50枚±1.06枚、3.87枚±1.34枚,其中可用卵母细胞数分别为1.70枚±0.57枚、1.86枚±0.55枚、2.06枚±0.63枚和1.67枚±0.50枚;4个季度卵母细胞成熟率分别为：（81.5±6.2）%、（70.7±5.6）%、（70.7±9.3）%和（77.0±6.9）%。以上结果表明,在每个卵巢平均获卵母细胞总数上,4—6月份、7—9月份两季度显著高于10—12月份（P〈0.05）,其他季节间没有显著性差异（P〉0.05）;7—9月份每个卵巢平均获可用卵母细胞数最高,显著高于1—3月份和10—12月份（P〈0.05）,但与4—6月份之间没有显著性差异（P〉0.05）;4个季度不可用卵母细胞数之间没有差异（P〉0.05）;4个季度卵母细胞的体外成熟能力上也没有显著差异（P〉0.05）。     

Inhibition of the development of Trichostrongylus spp. as third stage larvae in sheep

In non-lactating Frisian ewes slaughtered in September and November 1975 and in ewes slaughtered in March/April 1976 at lambing, the majority of Trichostrongylus axei, T. vitrinus and T. colubriformis found were inhibited third stage larvae (L₃). However, some larvae at various stages of development were found in the animals slaughtered at lambing. In contrast, in lactating ewes slaughtered 6 weeks after lambing in April 1976, almost all Trichostrongylus spp. appeared to be adults. All ewes grazed a pasture heavily contaminated with gastro-intestinal nematodes from June 1975 until at least 2 weeks before necropsy.In lambs on the pasture from April or June 1975, and slaughtered in September and November 1975 and March 1976 after at least 2 weeks of isolation, only small proportions of the Trichostrongylus spp. populations appeared to be L₃. Similar results were obtained from tracer lambs kept at pasture from August 1975 to March 1976. The implications of these findings are discussed.     

Effect of condensed tannins on egg hatching and larval development of Trichostrongylus colubriformis in vitro

The effects of condensed tannins extracted from seven forages on the viability of the eggs and first stage (L1) larvae of the sheep nematode Trichostrongylus colubriformis were evaluated in in vitro assays. The extracts of condensed tannins were obtained from Lotus pedunculatus (LP), Lotus corniculatus (LC), sulla (Hedysarum coronarium), sainfoin (Onobrychus viciifolia), Dorycnium pentaphylum (DP), Dorycnium rectum (DR) and dock (Rumex obtusifolius). Extracts containing 200 to 500 microg/ml reduced the proportion of eggs that hatched. The larval development assay was used to evaluate the effect of the extracts on the development of either eggs or L1 larvae to L3 infective larvae. Development was allowed to proceed for seven days by which time the larvae in control incubations had reached the infective L3 stage. Extracts containing 200 microg/ml from LP, DP, DR or dock prevented egg development, and only 11, 8 and 2 per cent of the eggs developed to L3 larvae with extracts from LC, sulla and sainfoin, respectively. When the concentration was 400 microg/ml no eggs developed to L3 larvae. The addition of the extracts after hatching also inhibited the development of L1 to L3 larvae; 200 microg/ml extracted from LP, LC, sulla, sainfoin, DP, DR and dock resulted in only 14, 18, 17, 15, 14, 16 and 4 per cent of L1 larvae developing to the L3 stage compared with 85 per cent for controls, and 400 microg/ml further reduced the development of L1 larvae. Statistical analyses showed that when the extracts were added before hatching they were significantly (P<0.001) more effective at inhibiting the larval development than when they were added after hatching. The condensed tannins from dock had the greatest inhibitory effect on egg development followed by the tannins from DR, sainfoin, DP, LP, sulla and LC.     

Direct measurement of dispersal of Dictyocaulus viviparus in sporangia of Pilobolus species

Dispersal of Dictyocaulus viviparus larvae by Pilobolus sporangia was studied on 29 faecal pats deposited between the end of June and late October 1988. Faecal pats were covered daily from day 3 to 4 after deposition with a large petri dish to measure the numbers of sporangia released and the numbers of larvae carried. The yield of both was variable. Dispersal of lungworm larvae was lowest on over-grazed pasture or when Pilobolus growth was very poor. When faecal pats were sheltered by a long sward, 17 per cent or more of larvae present at deposition were transported in this manner. In July and August, peak dispersal of lungworm larvae was on day 5, in September on day 6 and in October on day 7, the increasing time intervals being probably associated with decreasing temperature.     

Dynamics of infestation of cattle and pasture by gastrointestinal nematodes in an Atlantic temperate environment

The objective of the present study was to determine the dynamics of infestation of cattle and pasture by gastrointestinal nematodes in a mild humid environment in northwestern Spain. For this, infestation of pasture by free-living stages (L3), dynamics of faecal egg output, blood pepsinogen levels and worm burden in slaughtered animals were quantified. The results showed a high degree of annual variability, which was dependent on weather conditions. The seasons were clearly defined in the study area, with mild humid winters and relatively dry summers registered throughout the years of the study. Infestation of pasture by larvae varied from year to year, peaking during August in the first year, between August and December in the second year, and during October in the third year. The annual variation was mainly due to weather conditions, particularly the amount of rain in summer. The patterns of faecal egg output were similar in the first and third grazing seasons, with maximum levels observed in May/June; however, in the second year, the peak was reached in October. Blood pepsinogen levels increased from pasture turnout (March/April) until the end of the grazing season (November/December), reaching maximum values from August/September onwards. The nematode parasite species identified at necropsy were Ostertagia osteragi, O. lyrata, Cooperia oncophora, C. macmasteri, C. punctata and Trichuris ovis, with O. ostertagi and C. oncophora predominating. In faecal cultures, the following genera were also identified: Haemonchus, Trichostrongylus, Nematodirus, Bunostomum, Oesophagostomum and Strongyloides. There was a significant correlation (r=0.97, P<0.01) between worm burden (Ostertagia spp.) and pasture infestation (Ostertagia L3) 3 weeks prior to slaughter of the calves, and also between blood pepsinogen levels and pasture infestation by Ostertagia L3 (r=0.33, P<0.02). Correlations between worm burden and faecal egg output and between blood pepsinogen level and faecal egg output were not significant. The results obtained in the present study confirm that there is annual variability in the time-course of nematodosis in cattle, and demonstrate the importance of weather, particularly summer rainfall, in an Atlantic temperate environment.     

Occurrence of second and third instars of Gasterophilus intestinalis and Gasterophilus nasalis in stomachs of horses in Kentucky.

The occurrence of 2nd and 3rd instars of Gasterophilus intestinalis and Gasterophilus nasalis was determined in 476 horses during the 22-year period from 1951 to 1973. Overall, G intestinalis infected 98.7% of the horses and averaged 168/horse; whereas G nasalis infected 80.7% of the horses and averaged 52/horse. Aggregate average total numbers for G intestinalis ranged from a low of 50 in September to a high of 229 in March, and for G nasalis, from a low of 14 in September to a high of 82 in February. Horses were infected by 2nd or 3rd instars of both species on a year-round basis. Differentiation between the instars provided insight into the dynamics of the infections. For G intestinalis, the data indicated (1) 2nd instars from the previous year's generation of flies continue to arrive in the stomach until April; (2) arrival of the current year's crop of 2nd instars starts in July; and (3) 3rd instars from the previous year's generation of flies are not voided in appreciable numbers until August, when numbers of the current year's crop of 3rd instars appear in the stomach. For G nasalis, the data indicated (1) arrival in the stomach of the current year's generation of 2nd instars starts in July and terminates in January and (2) 3rd instars from the previous year's generation of flies are voided over a period beginning in March and extending into August, when the current year's crop of 3rd instars begin to appear. Acquisition of infections of horses with G intestinalis is nearly a year-round process, except for April, because of the persistence of viable larvae in eggs for a prolonged period after development and fly activity has ceased in the fall. In contrast, infection with G nasalis is interrupted between December and May, because eggs hatch naturally after a short period of development, and fly activity ceases in the fall.     

Ixodid ticks on cattle belonging to small-scale farmers at 4 communal grazing areas in South Africa

Ixodid ticks were collected during the period September 1991 to August 1993 from cattle belonging to small-scale farmers utilising 4 communal grazing areas. Three of these were in North West Province and 1 in Mpumalanga province, South Africa. Ten tick species were collected in North West Province and 7 in Mpumalanga. The adults of Amblyomma hebraeum, Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi were most numerous in North West Province, while in Mpumalanga Boophilus decoloratus comprised more than 75% of the total population. Amblyomma hebraeum was present on all grazing areas, and heavy infestations of adults occurred during the period October to May on 1 of these. Few B. decoloratus were collected in North West Province, chiefly because the sampling method was inadequate, and most of these were present during early summer (October to December) and late summer and autumn (March to May). The initially low population of B. decoloratus in Mpumalanga increased substantially towards the conclusion of the survey, probably because of the cessation of dipping. Boophilus microplus was present in small numbers on 2 grazing areas in the North West Province. Adult Hyalomma marginatum rufipes reached peak numbers from December to February and Hyalomma truncatum from February to April in the North West Province. Only H. marginatum rufipes was collected in Mpumalanga. Rhipicephalus appendiculatus was present on all the grazing areas, with most adults present from December to April. Most adult Rhipicephalus evertsi evertsi were collected from September to April and Rhipicephalus simus was present during the period October-April.     

Epidemiology of ovine oestrosis (OEstrus ovis Linné 1761, Diptera: Oestridae) in Sicily

A survey for oestrosis was carried out in the slaughterhouse at Messine (Sicily) from May 1996 to April 1998. The heads of sheep from local flocks were collected each month. A total of 841 heads were examined according to a validated procedure. 469 (55.8%) were infested by OEstrus ovis larvae. 4423 larvae were harvested: 1829 first instar larvae or L1 (41.4%), 1286 second instar larvae or L2 (29.1%) and 1308 third instar larvae or L3 (29.6%). The mean larval burden for infected sheep was 9.4 larvae with an average of 3.9 L1, 2.7 L2 and 2.8 L3. No period of hypobiosis was recorded. The proportions of larvae in each of the different larval stages was similar from January to September, however, from October to December the percentage of L1 was higher, indicating a period of slowed development. In order to lower the overall prevalence of this disease, it would be necessary to use a parasiticide effective against O. ovis, for all routine parasite control treatments.     

Ixodid ticks of angora and boer goats,grysbok, common duikers,kudus and scrub hares in Valley Bushveld in the Eastern Cape Province,South Africa

At monthly intervals from February 1983 to January 1984 two Angora goats, two Boer goats, one grysbok, Raphicerus melanotis, one common duiker, Sylvicapra grimmia, one greater kudu, Tragelaphus strepsiceros, and four scrub hares, Lepus saxatilis, were killed on a farm in Valley Bushveld in the Eastern Cape Province, South Africa and examined for ticks. Seven ixodid tick species were collected, of which Rhipicephalus glabroscutatum followed by Amblyomma hebraeum and Rhipicephalus oculatus were the most numerous. Amblyomma hebraeum was mainly a parasite of the two goat breeds, with the Angora goats harbouring greater numbers than the Boer goats, while large numbers of R. glabroscutatum parasitized the goats and the antelopes. Rhipicephalus oculatus was nearly exclusively a parasite of scrub hares. The larvae of A. hebraeum were most numerous on goats from May to July, the nymphs from September to November and the adults from August to December and during February, while the immature stages of R. glabroscutatum were most numerous on these animals from April to July and the adults from August to December. Peak activity periods of the latter tick were somewhat longer on kudus than on goats; the immature stages were most numerous from January to August and the adults from July to February. The larvae of R. oculatus were most numerous on scrub hares from March to May, nymphs from September to November and adults from October to December.     

Parasites of domestic and wild animals in South Africa. XXXIX. Helminth and arthropod parasites of Angora goats in the southern Karoo

Parasites were collected from 160 Angora goats and kids on the Jansenville Experimental Farm, Eastern Cape Province. Six nematodes were identified to species level and three to generic level. Nematodirus spathiger was the most numerous of the economically important nematodes recovered. It was always present, and fourth stage larvae were collected from untreated goats from August to March, while animals used as tracers also picked up most infection from August to March. Kids born on the farm during October acquired their first nematode infections between 2 and 3 months of age and the intensity of infection increased erratically thereafter to reach a plateau once the kids were 14 months of age. Eight of the nine kids between 3 and 5 months of age and examined between January and March were infected with Moniezia expansa. Five ixodid tick species were collected from the goats of which Rhipicephalus glabroscutatum was the most numerous and prevalent. Its immature stages were present mainly from March to September and adults from July to January. The goats also harboured the biting louse Damalinia limbata and the sucking louse Linognathus africanus. The greatest intensity of infestation with L. africanus occurred on the kids during the first few months of their lives. The larvae of the nasal bot fly, Oestrus ovis were present in kids at 1 month of age, and infestation took place mainly from spring to late summer.     

Species composition of Gasterophilus spp. (Diptera, Oestridae) causing equine gastric myiasis in southern Italy: parasite biodiversity and risks for extinction

Horse gastrointestinal myiasis caused by larvae of Gasterophilus spp. (Diptera, Oestridae) flies has a worldwide distribution and, where present, it is primarily caused by larvae of Gasterophilus intestinalis and Gasterophilus nasalis. Other species, i.e., Gasterophilus inermis, Gasterophilus pecorum and Gasterophilus haemorrhoidalis, present in different or in the same regions of the gastrointestinal tract, were only occasionally reported in very limited areas of eastern European Countries and in central Italy. With the aim to contribute data on the species composition of Gasterophilus and on the seasonal variation of the infection pattern in southern Italy, 152 native horses were necropsied from January to December 2003 and Gasterophilus larvae were collected from the stomach, the small intestine and the rectum of each of them. On the whole, 125 (82.2%) horses were infected by larvae of Gasterophilus spp. and 214 second stage larvae (L2) and 13,342 third stage larvae (L3) collected. Five species of Gasterophilus were identified with the following prevalence: G. intestinalis=95.2%, G. nasalis=44.8%, G. inermis=15.2%, G. pecorum=2.6% and G. haemorrhoidalis=0.8%. L3 were retrieved throughout the observation period with the highest mean burdens from January to August 2003 while the lowest mean was registered from September to November 2003. L2 were collected in February-March 2003 and from September to December 2003. The majority of the animals (n=66, 43.4%) were infected with a single Gasterophilus species, however, 45 animals (29.6%) harboured 2 species, 12 animals (7.9%) 3 species and 2 animals (1.3%) 4 species. The trend of abundance in the L3 of G. intestinalis and G. nasalis, the most represented species, was highly concordant (r=0.5, p<0.001). A retrospective comparison of our results and of other data from four seasons of observation (1983-1986) in central Italy showed that the number of G. inermis, G. pecorum and G. haemorrhoidalis have been decreasing relative to G. intestinalis and G. nasalis which may suggest tendency toward the extinction of the three former species of Gasterophilus.