Development and survival ofHaemonchus contortus andTrichostrongylus sp. on pasture in Cameroon

Summary The development and survival ofHaemonchus contortus andTrichostrongylus sp. on pasture at Bamenda, Cameroon were studied by spreading faeces containing strongyle eggs from mixed infections on 12 experimental grass plots from April 1988 to March 1989. Development of eggs to infective larvae during the rainy season (April to October) took place within one week. The infective larvae ofH. contortus survived for 11±2 weeks (with a range of 7 to 13 weeks) during this period while those ofTrichostrongylus sp. survived for 9±2 weeks (with a range of 6 to 12 weeks). No larvae were recovered from eggs spread on pasture during the dry season, except in December when unseasonal rains fell within 9 days of spread of the faeces. Rainfall was identified as the most important climatic condition affecting the development and survival of infective larvae on pastures at Bamenda.

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Desarrollo Y Supervivencia DeHaemonchus Contortus YTrichostrongylus Sp. En El Pasto En Camerún

Resumen Se estudió el desarrollo y supervivencia deHaemonchus contortus y trichostrongylus sp. en el pasto en Bamenda (Camerún) extendiendo heces contaminadas en 12 parcelas experimentales entre abril de 1988 y marzo de 1989. Durante la época húmeda, el desarrollo hasta larvas infestantes tardó una semana. Las larvas infestantes deH. contortus sobrevivieron 11±2 semanas (rango de 7 a 13 semanas), mientras que las larvas deTrichostrongylus sp. sobrevivieron durante 9±2 semanas (rango de 6 a 12 semanas). Durante la época seca no se recuperó larva, con la excepción del mes di diciembre, durante el cual se produjeron lluvias inesperadas en los 9 días siguientes a la extensión de las heces. La lluvia fue identificaada como el factor climático más importante en lo relativo al desarrollo y supervivencia de larvas infestantes en el pasto en Bamenda.

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l'Etude Du Developpement Et De La Survie De Haemonchus Contortus Et De l'Espece Trichostrongylus Sur Les Paturages Au Cameroun

Résumé L'étude du dévéloppement et de la survie deHaemonchus contortus et de l'espèceTrichostrongylus sur les pâturages à Bamenda, Cameroun s'est faite par arrosage depuis le mois d'Avril 1988 à Mars 1989 de 12 partitions expérimentales de gazon avec des fécès contenant des oeufs de strongyles provenant d'une infection mixte. Le dévéloppement des oeufs jusqu'au stade larvaire infectieux pendant la saison des pluies (Avril–Octobre) s'est déroule en une semaine. La larve infectieuseH. contortus survécut pendant 11±2 semaines (dans une intervalle de sept à 13 semaines) au cours de cette période, contre 9±2 semaines pour l'espèceTrichostrongylus (avec une durée s'étalant de six à 12 semaines). Aucun dévéloppement larvaire n'a eu lieu à partir des oeufs arrosés sur les pâturages pendant la saison séche, excepté en Decembre lorsque des pluies non saisonnieres tombèrent au cours des neuf jours suivent l'arrosage des fécès. La pluviometrie parut etre le facteur climatique le plus important favorisant le dévéloppement et le survie des larves infectieuses sur les pâturages à Bamenda.

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Present address: Faculty of Science, University of Buea, S.W. Province, Cameroon.     

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.     

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.     

Use of disophenol for the control ofHaemonchus contortus in sheep in west java,Indonesia

Summary The result of a field trial investiguting the anthelmintic effect of disophenol againstH. contortus in sheep raised under Asian small farming practice is reported. It was clearly shown that a single injection of disophenol suppressed the numbers ofH. contortus to very low levels for periods up to 3 months despite the presence of large populations ofH. contortus infective larvae available on pasture and herbage grasses.

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Uso Del Disofenol Para El Control DeHaemonchus Contortus En Ovejas En El Oeste De Java, Indonesia

Resumen Se describen los resultados de un trabajo de campo, en donde se investigó el efecto anti helmíntico del disofenol contra elH. contortus, en ovejas criadas en minifundios.Se demostró claramente que, una sola inyección de disofenol, redujo sensiblemente el número deH. contortus por períodso de 3 meses, a peser del gran número de larves infectivas presentes en el pasto.

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Le Disophenol Dans La Lutte ContreHaemonchus Contrortus Chez Le Mouton A L'est De Java, En Indonesie

Résumé Les résultats obtenus lors d'essais expérimentaux sur l'effet anthelminthique du Disophenol contreH. contortus chez des moutons élevés suivant les formules des petits élevages asiatiques sont rapportés.Il a été clairement démontré qu'une seule injection de Disophenol ramène le nombre deH. contortus à de très bas niveaux pendant une période de 3 mois en dépit de la présence de nombreuses populations de larves infectieuses deH. contortus présentes dans les pâturages et plantations fourragères.

     

The effect of transfer factor treatment on two challenge infections ofHaemonchus contortus in immuno-competent 7-month-old lambs

A number of immuno-competent Blackface lambs were infected with 10,000Haemonchus contortus third stage larvae and were later challenged with a second dose of 10,000H. contortus third stage larvae. One group of lambs was treated with dialysed transfer factor prior to the second challenge dose.Histological changes in the abomasal wall, reductions in abomasal worm burdens at slaughter and faecal egg counts monitored throughout the experiment suggested the presence in some animals of (1) an innate resistance, (2) a self curing effect, (3) an enhancement of this self curing effect in the transfer factor treated group and (4) a response in one transfer factor treated animal comparable to classical self cure.     

Development and survival of Haemonchus contortus infective larvae derived from sheep faeces under sub-tropical conditions in the Potohar region of Pakistan

Assessment on the development and survival of Haemonchus contortus larvae was made to evaluate the influence of microclimatic variables viz., relative humidity (%), temperature (°C), rainfall (mm) and intensity of sunlight (hrs). Pasture plots in a sub-tropical area, Pakistan were contaminated with H. contortus eggs at the start of every month. The plots were sampled on fortnightly basis after contamination for three consecutive months. The overall pattern indicated the most favorable conditions for survival, development and translation to herbage was during the wet season from July to October and the least favorable was during the dry season from April to June. Peak infective larvae (L₃) recovery was during the 15–45 day interval for each plot and the lowest number was during the 75–90 day interval. Herbage was collected in the morning, afternoon and evening and greatest recovery of L₃ was in the morning time and least in the afternoon. The number of L₃ on pasture was directly related to the pattern of rainfall and relative humidity with a significant (P < 0.05) positive correlation and temperature and intensity of sunshine were negatively correlated (P < 0.05). The results suggest that pastures can remain infective for up to 2 months and become relatively clean by 90 days after contamination. Thus, long pasture rest periods, especially during the high risk wet season, may be a helpful strategy to reduce the infection levels.     

Seasonal changes in the prevalence ofHaemonchus andTrichostrongylus hypobiotic larvae in tracer goats in Malaysia

An investigation into the seasonal changes in the population structure of Haemonchus and Trichostrongylus in tracer goats was conducted over 12 months at Serdang, an area in southern West Malaysia with year-round tropical rainfall. Successive groups of parasite-free tracer goats were grazed for a month alongside naturally infected adult goats and necropsied for worm counts 14 days after their removal from pasture. No hypobiotic larvae of Trichostrongylus were recovered. Hypobiotic larvae of Haemonchus were evident during each month of the year but accounted for only a very small proportion of the total Haemonchus burden. Very low levels were encountered from December through to June. Comparatively higher levels of hypobiosis were observed thereafter with a peak of 7.4% in September. The factors responsible for hypobiosis were not clearly defined but the phenomenon was associated with increasing levels of soil moisture storage. Host resistance, adult worm population of tracers and population of ingested L3 were ruled out as possible inducing factors.     

Feasibility of herbage sampling in large extensive pastures and availability of cattle nematode infective larvae in mountain pastures

Herbage sampling has been used to ascertain the contamination and epidemiology of cattle nematode infective in large extensive pastures situated in the centre of France, where heifers graze for four months on a total area of one ha/heifer in mountains at 1200 or 1400 m above sea level. The sampling was done for each paddock in four virtual “hectares”, tufts of grass being picked both close to faecal pats or “refusals”, and far from these pats.Ostertagia was the predominant parasite and the occurrence of Dictyocaulus resulted from silent-carrier heifers. Just after the thawing of the snow, when the heifers arrived in the mountains, the contamination was very high: 8000–9000 L3 and 45.00 to 63.00 L3 kg^?1 dry herbage, respectively, far from and close to faecal pats, but this contamination decreases regularly during the season.The sampling of four areas (four “hectares”) in each paddock was found to be a very valuable method. The variation of the mean was low and found mainly when the number of larvae was high (6–19% only for the spring sampling).This technique could have some merit in parallel or concurrently with tracer calves which are always difficult and expensive to use.     

Studies on Haemonchus contortus. X. The effect of Trichostrongylus axei in Merinos on artificial pastures

A recently established Eragrostis curvula pasture 1,1 ha in size at Hennops River in the Transvaal Highveld was contaminated from 6 October 1976 until 20 May 1977 by 30 weaned Merinos, each infested with 7 000 infective larvae of H. contortus. On 2 November 1976 3 groups of weaned Merinos and again on 10 January 1977 a further group of Merinos were infested with 40 000 infective larvae of Trichostrongylus axei. From 19 November a single group of sheep, predosed with T. axei, and a control group grazed with the seeders for 8 weeks. After 6 weeks another group of sheep dosed with T. axei grazed with them, thus ensuring a 2-week overlap. This continued until autumn, when the last groups were removed. Efficacy against challenge reached Class C (greater than 50% effective against total worm burdens of H. contortus in greater than 50% of sheep) in early summer and autumn, but only reached significant levels of either P less than 0,01 or P less than 0,05 in summer. Peak worm burdens in controls were recorded in early autumn.     

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.     

Studies on Haemonchus contortus. XI. The effect of a bovine strain of Trichostrongylus axei in Merinos on natural pastures heavily infested with H. contortus

Sheep grazed on natural pastures heavily infested with infective larvae of Haemonchus contortus. Sixty-eight weaned Merinos were divided into 6 groups on Day 0 (23 November 1977), and on Day +14 (7 December) 79 Merinos were divided into 7 groups. There were 2 groups of undosed controls and other groups were either dosed with infective larvae of Trichostrongylus axei (bovine strain) only on Days 0 and +14, or in combination with H. contortus, or with subsequent doses of H. contortus, 28 days later. One group (Group 12) was dosed with T. axei and treated with a subcutaneous injection of di-iodonitrophenol (DNP) on Day +14. With the exception of 2 sheep, the sheep of the first 6 groups survived until slaughter in March and April 1978, while many sheep (43) of the latter 7 groups died or were killed in extremis from March-May. T. axei dosed on 23 November (Day 0) protected Group 2 by greater than 50% in greater than 50% of sheep. In the latter 7 groups the best results were achieved when DNP was combined with predosing with T. axei. The poor results were probably due either to delayed predosing with T. axei or a massive challenge in the wettest summer on record.     

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.     

Development and survival of infective larvae of gastrointestinal nematodes of cattle on pasture in central Kenya

On a series of pasture plots, 2 kg pats of bovine faeces containing known numbers of strongylid (Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus) eggs were deposited at intervals of 4 weeks from July 1995 to June 1996. The plots were sampled every 2 weeks after contamination and infective larvae were identified and counted. Larvae of all the genera developed throughout the year, but the pats exposed during the rainy season yielded more abundant larvae on the herbage. Irrespective of the season of deposition of the pats, larvae were found in larger numbers from 2 to 6 weeks after deposition and generally declined to below detectable levels within 12 to 16 weeks of contamination. The comparatively short survival times noted in this experiment may present opportunities for manipulation of the population dynamics of the gastrointestinal nematodes in the tropical environment of Kenya.     

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.