Protection of lambs with a purified metabolite of exsheathed third-stage Haemonchus contortus larvae

Helminth-free lambs (approx 4 months old) were inoculated SC with a purified metabolite of exsheathed third-stage Haemonchus contortus larvae. The metabolite was obtained from in vitro cultivation and was identified as XL3FA1. After 3 periodic XL3FA1 inoculations, lambs were challenge exposed with H contortus. Multiple vaccinations with XL3FA1 did not inhibit the development of worm populations in the lambs; however, worm egg production seemed to be inhibited.     

Development and survival of Haemonchus contortus larvae on pasture at Vom,Plateau State,Nigeria

The development and survival of the eggs of Haemonchus contortus on pasture at Vom were studied by depositing faecal pellets on grass plots over a period of 12 months. Development and survival to the infective larvae occurred throughout the study except during the dry season months of December to April. More infective larvae were recovered from the herbage in June, July and August than in other months. The survival time of the infective larvae ranged from 2 weeks in October to 10 weeks in June, July and August. Rainfall was the most important epizootiological factor influencing the development and survival of the infective larvae. Temperature was not a limiting factor.     

Lack of effects of quebracho and sainfoin hay on incoming third-stage larvae of Haemonchus contortus in goats

The effects of tannins on adult populations of Haemonchus contortus, Trichostrongylus colubriformis and Teladorsagia circumcincta in goats are characterised mainly by a decrease in egg excretion without any significant changes in worm number. In contrast, the impact of tannins on T. colubriformis or T. circumcincta third-stage larvae (L3) is associated with a significant reduction in worm establishment. The objective of the present study was to examine the effects of quebracho extract tannins on H. contortus L3. The consequences of consumption of sainfoin hay were also examined. Twenty-one na?ve kids were divided into three experimental groups. Group Q received quebracho extract and group S received sainfoin hay from days D3 to D5. Group C remained as an infected control group. All kids received 1500 L3 H. contortus on D0, D1 and D2. On D18, post-infection, the kids were slaughtered and the worm populations compared in the different groups. Compared to the control values, the worm counts decreased, respectively, by 33% and 38% in groups Q and S but the differences were not significant. No differences were found in pathophysiological measurements between the three groups. The results confirm differences in tannin effect according to nematode species but not parasitic stage.     

捻转血矛线虫感染性三期幼虫gst基因的筛选及抗干燥功能分析

为研究干燥作用对捻转血矛线虫L3期幼虫mRNA表达的影响,筛选并分析干燥相关表达基因,本试验利用mRNA差异显示技术得到了捻转血矛线虫干燥相关基因,通过相对荧光定量PCR验证所获基因的表达情况,并在秀丽隐杆线虫中通过RNA干扰抑制相关同源基因的表达检测干燥后复苏虫体生存率以研究基因抗干燥功能。结果显示,差异表达序列GH-U02A与已知捻转血矛线虫谷胱甘肽-S-转移酶(GST)氨基酸同源性为94%。对秀丽隐杆线虫Ce-gst-7基因进行RNA干扰后,虫体在干燥后的生存率降低,证明gst基因在线虫中有抗干燥功能。     

利用mRNA差异显示技术分离捻转血矛线虫感染性三期幼虫抗干燥相关基因

捻转血矛线虫感染性三期幼虫对干燥环境具有很强的抵抗力,环境适宜时可恢复到正常状态并继续感染宿主.为初步探讨捻转血矛线虫感染性三期幼虫抗干燥的分子机制,试验对该期幼虫施以不同干燥条件的处理,筛选出虫体存活率达到90％的干燥条件.在筛选到的条件下(相对湿度为50％,时间为60 h)处理虫体,采用mRNA差异显示技术分析干燥环境下培养的虫体和正常虫体的mRNA表达差异.经验证获得了48个差异表达的EST序列,其中25个(52.08％)序列与现有捻转血矛线虫基因组数据库有高度同源性;15个(31.25％)序列与已知线虫的cDNA序列或基因组序列有较高同源性;9个(18.75％)序列与其他线虫已知蛋白质氨基酸序列同源性较高.差异表达序列AF-U01C与多种线虫的蛋白酶体β亚基家族成员同源性达90％,差异表达序列AG-U01A与多种线虫的β酮脂酰CoA硫解酶(3-ketoacyl-CoA thiolase)同源性达65％.结果为进一步研究寄生性线虫抗干燥机制奠定基础.     

The effect of ageing on the antigenicity of Haemonchus contortus larvae.

Viable Haemonchus contortus larvae used as a source of antigen in complement fixation tests showed a decrease in antigenic potency following storage for approximately two months at 5 degrees C. In contrast, larvae killed by freezing and stored at --15 degree C showed no such decline over a similar period. It is suggested that this loss of potency with ageing may be partly responsible for increased worm populations in sheep in spring.     

The possible fate of crystal harbouring larvae of Haemonchus contortus.

An examination of the occurrence of crystalline inclusions in the intestinal cells of fourth and fifth stage Haemonchus contortus revealed that a high percentage of inhibited early fourth stage larvae (L4) and developing L4 and a lower percentage of early fifth stage larvae (L5) harboured these crystals. Before the fourth moult crystals were falling into pieces, indicating that worms harbouring crystals can develop further. The presence of crystals may be associated with a retardation of development.     

Development and survival ofhaemonchus contortus larvae on pasture in iraq

The survival of Haemonchus contortus infective larvae on pasture and soil was studied over a period of 12 months in the Baghdad area. Infective larvae were found on herbage and soil at all times except in the summer months. During autumn and winter infective larvae in pasture survived for periods of up to 32 weeks. Little larval migration into soil was observed during this study and larvae did not survive for long in the faecal pellets during the summer.     

Studies on Haemonchus contortus. IX. The effect of Trichostrongylus axei in Merinos on natural pasture

Four groups of 6-7-month-old Merino lambs were each dosed with 40 000 infective larvae of Trichostrongylus axei on 2 November 1976 and subsequently exposed to challenge with Haemonchus contortus on natural grazing at the University of Pretoria's Experimental Farm in the eastern suburbs of Pretoria. One of these groups and one group of controls were killed every 8 weeks from the end of December 1976-June 1977. Predosing with T. axei was greater than 50% effective against 5th stage and adult H. contortus in greater than 50% of sheep for 164 days (Class C), improving to greater than 60% in greater than 60% of sheep (Class B) 220 days after dosing T. axei. The numbers of retarded 4th stage larvae (L4) of H. contortus in the undosed controls as well as in the sheep predosed with T. axei rose from a low level in summer (December) to a peak in late Autumn (June).     

Studies on Haemonchus contortus. XII. Effect of Trichostrongylus axei in Dorper lambs on natural pasture lightly infested with H. contortus

Weaned Dorper lambs on natural pasture were predosed with 40 000 infective larvae (L3) of Trichostrongylus axei, irradiated (0,3 kGy) L3 of T. axei or closantel at 10 mg/kg either in September or November 1978 and were compared with Merino yearlings predosed with 40 000 L3 of T. axei in November 1977. The following summer (December-March) only 178,6 mm of rain fell and very few H. contortus were present on pastures. Artificial challenge with 20 000 L3 of Haemonchus contortus with the local strain from the University of Pretoria's experimental farm was given 6-7 months after predosing with T. axei. When compared with the controls, significant reductions occurred only in Group 11 (T. axei irradiated at 0,3 kGy on Day +63) (P = 0,025); Group 2 (T. axei on Day 0) (P = 0,003) and Group 4 (T. axei and closantel on Day 0) (P = 0,049). We concluded that predosing with T. axei was unsuccessful in Dorpers and Merinos artificially challenged 6-7 months later with H. contortus.     

Development and survival of Haemonchus contortus isolated from sheep on a pasture at Bunia (Itiri, Zaire)]

Development and survival of Haemonchus contortus larvae were studied from December 1987 to November 1988 during three different periods (dry season, first and second rainy seasons) on an experimentally infected pasture at Bunia (Ituri, Za?re). Whatever the season, eggs developed into infective larvae within six days and the largest number of larvae on the herbage occurred between the 12th and the 18th day post deposition. However, the two rainy seasons were the most favourable for transmission because of the high number of larvae on the pasture and the increased survival of these larvae after 4 weeks.     

Investigation of Haemonchus contortus infections in sheep. Comparison of irradiated larvae and transfer factor treatment

A comparison is made between the resistance conferred to Haemonchus contortus challenge by irradiated larval treatment and transfer factor (TF) treatment in four-month-old lambs and seven-month-old lambs. As in previous investigations the irradiated larval treatment failed to confer resistance to the four-month-old lambs challenged with 10,000 third stage larvae while similar irradiated larval treatment in seven-month-old lambs reduced the worm burdens by 40 per cent compared to controls. The TF treatment produced a 34 per cent reduction in the challenge infection in the four-month-old lambs and a 45 per cent reduction in the seven-month-old lambs compared to the control lambs. It is concluded that TF activity operates independently of immune competence.