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1.
Rhesus monkeys inoculated subcutaneously with 800-2500 cercariae of Schistosoma incognitum did not yield adult worms. Percutaneous exposures, however, resulted in the presence of adult flukes 21-35 days post infection. The infection became very mild (0-4 flukes) 45-100 days after exposure and no eggs were excreted. Monkeys percutaneously exposed to cercariae of Orientobilharzia dattai and treated with prednisolone yielded a very small number of flukes 22 days after exposure while non treated controls yielded no adult worms.  相似文献   

2.
Although the effect exerted on fish by fluke cercariae developing in fish as intermediate hosts is fairly well known, cercariae of flukes requiring intermediate hosts other than fish occur in fish ponds in much higher numbers. To study the effect of these latter cercariae on fish fry, a few days old common carp fry (Cyprinus carpio) were exposed to cohorts of xiphidiocercariae or echinocercariae shed by one or two snails acting as intermediate hosts. The observed pathogenicity of these cercariae was compared to the well-known pathogenic effect of Diplostomum cercariae. Although Diplostomum cercariae proved to be the most pathogenic, occasionally also the other two types of cercariae could kill the common carp fry by invading their body. Xiphidiocercariae ingested by the fish penetrated the intestinal wall and developed into metacercariae within the body of the fry. They could also get into the musculature through the skin. The much larger echinocercariae invaded the gill cavity where they became encapsulated, thus hampering gill function and leading to fish mortality due to oxygen deficiency. Diplostomum cercariae were more pathogenic than the cercariae of the other two flukes in that they were shed by the intermediate host in very large numbers. Although much less xiphidiocercariae and echinocercariae emerged from the intermediate host snails than Diplostomum cercariae, the former could kill the fish fry already in lower numbers. These findings prove that fluke cercariae nonspecific to fish may exert pathogenic effects on fish, and presumably contribute to the early mortality of young fry placed out into fish ponds.  相似文献   

3.
Objective To determine the effect of treating naturally acquired gastrointestinal nematode and paramphistome infections on milk production in dairy cattle.
Design A field trial.
Animals One thousand two hundred and thirty nine dairy cows.
Procedure Cows were either not treated or treated with 4.5 mg/kg oxfendazole, 16.6 mg/kg oxyclozanide or 4.5 mg/kg oxfendazole and 16.6 mg/kg oxyclozanide in March, May and August.
Results A significant increase in milk production, averaging 0.4 L (SE 0.2) per day, was seen when dairy cows infected with gastrointestinal nematodes and paramphistomes were treated with oxfendazole or oxfendazole and oxyclozanide in March, May and August. Cows treated with oxyclozanide alone at these times produced no more milk than untreated cows.
Faecal egg counts confirmed that oxyclozanide treatment reduced paramphistome populations and oxfendazole treatment reduced nematode populations in cows over the 7-month monitoring period.
Conclusion When dairy cows infested with gastrointestinal nematodes and paramphistomes were treated with oxfendazole alone or oxfendazole and oxyclozanide in March, May and August milk production increased.  相似文献   

4.
Calves immunized with adult Mecistocirrus digitatus implanted directly into the abomasum did not develop a substantial degree of immunity to a subsequent large oral (challenge) dose of larvae, which developed to maturity. In contrast animals immunized by oral infection developed strong resistance. The calves implanted with adult worms appeared to show a greater degree of susceptibility to maturation of the challenge infection than controls which received a challenge of the same magnitude without any previous immunization. The implanted female adult worms established in the hosts and continued to produce more eggs for a longer time than those which developed to maturity from the oral immunizing infection with third-stage larvae. Passive haemagglutination studies revealed that the implanted adult worms stimulated little or no antibody response in the hosts. In the calves which did not show a response to the adult worm implant the subsequent challenge with an oral infective dose of third-stage larvae also failed to stimulate a response. Likewise the two calves from the group which showed a weak antibody response to the adult worm implant did not show an increased response when challenged. In contrast, calves immunized with an oral infection of third-stage larvae had an antibody response which showed a vigorous rise on challenge in four of the five calves. Thus a direct relationship between resistance to challenge infection and the antibody response determined by the passive haemagglutination and gel-diffusion tests was observed in the calves immunized orally.  相似文献   

5.
The complex life cycles of most trematode parasites include three hosts. The first intermediate host is a snail, the second is normally a teleost fish and a piscivorous bird serves as the definitive host. Lymnaeid snails are most likely to be responsible for cercarial shedding, which infect exposed fish and in turn are eaten by piscivorous birds. From 2008 to 2010 fish in the Okavango and Orange-Vaal River Systems were collected and dissected in order to determine the prevalence and intensity of larval trematode infections in the eyes and brains. This paper discusses the possible ecological factors which can influence the probability of certain fish species becoming infected with diplostomid cercariae and hence metacercariae. The feeding strategies and sizes of piscivorous birds, which could act as definitive hosts for the adult worms, are summarized and discussed. Information on the snail species responsible for furcocercous cercarial shedding in the two study sites is also included.  相似文献   

6.
Elk infected with the meningeal worm, Parelaphostrongylus tenuis (Protostrongylidae), do not consistently excrete larvae in feces, making the current method of diagnosing live animals using the Baermann fecal technique unreliable. Serological diagnosis could prove more useful in diagnosing field-infected animals but depends on the identification and availability of good quality antigen. To mimic field infections, 2 elk were inoculated with 6 infective L3 larvae of P. tenuis, and another 2 with 20 L3 larvae. Fecal samples were examined for nematode larvae using the Baermann technique and serum samples taken were tested for anti-P. tenuis antibody with ELISAs by using the excretory-secretory (ES) products of L3, and sonicated adult worms as antigens. One animal passed first-stage larvae in its feces 202 days postinoculation, but passed none thereafter. The remaining 3 inoculated animals did not pass larvae. In contrast to parasite detection, antibodies against larval ES products were detected in all animals starting from 14 to 28 days postinoculation and persisted until the termination of the experiment on day 243 in 2 animals that harbored adult worms. Antibodies against somatic antigens of the adult worm were not detected until day 56 but also persisted until the end of the experiment in the animals with adult worms. In 2 elk that had no adult worms at necropsy, anti-ES antibodies were detected transiently in both, while anti-adult worm antibodies were present transiently in one. These findings confirm the superiority of P. tenuis larval ES products over somatic adult worm antigens as serodiagnostic antigens, as previously observed in studies of infected white-tailed deer, and extend the application of the newly developed ELISA test in diagnosing and monitoring cervids experimentally infected with P. tenuis.  相似文献   

7.
Gastrodiscosis outbreaks due to Gastrodiscus aegyptiacus were recorded in horses in the vicinity of Harare, Zimbabwe, in the absence of Bulinus forskalii, B. senegalensis and Cleopatra sp. which are considered to be the only intermediate host snails. This suggested the possibility of other snail species acting as intermediate hosts in the life cycle of the trematode. A study was carried out to determine the susceptibility of 7 freshwater snail species to infection with G. aegyptiacus. First generation (F-1) of 5 freshwater pulmonate snail species, Bulinus tropicus, Bulinus globosus, Biomphalaria pfeifferi, Helisoma dyuri and Physa acuta that were bred in the laboratory, and 2 prosobranch snail species, Melanoides tuberculata and Cleopatra sp. that were collected from the field were used in this study. Data pertaining to mortalities and cercariae shedding were recorded throughout the experimental period. The prosobranch snails, M. tuberculata and Cleopatra sp. were susceptible to G. aegyptiacus with a minimum prepatent period of 45 days and 54 days, respectively. Bulinus tropicus, P. acuta and H. duryi were susceptible as evidenced by the presence of different generations of rediae and mature cercariae on dissection at 59 days post-infection although attempts to induce the snails to shed from 28 days post-infection did not produce cercariae. Bulinus globosus and Bio. pfeifferi were refractory to infection. The results revealed the ability of G. aegyptiacus to infect M. tuberculata, Cleopatara sp., B. tropicus, P. acuta and H. duryi under experimental conditions and this may explain the recorded outbreaks of gastrodiscosis in equine populations in Zimbabwe in the absence of the known intermediate hosts. Bulinus tropicus is considered as the most likely major intermediate host of G. aegyptiacus because of its wide distribution in Zimbabwe and is well adapted to a wide variety of environments.  相似文献   

8.
为探明广西南宁地区水牛体内前后盘吸虫的种类，通过对其肝脏来源虫体进行鉴定，确定水牛感染的具体种属。本研究对南宁市某屠宰场水牛肝脏进行剖检、病理观察，并采集肝脏内寄生的前后盘吸虫进行虫卵孵育，对孵育所得的虫卵及虫体进行形态观察，对成虫虫体进行HE及苏木素染色，观察其内部的结构，并采用分子生物学方法对成虫进行鉴定。结果显示，虫体感染的肝脏表面有出血点，且呈现淤血、化脓灶、肝脏肿大、质地偏软等肉眼可见病变。虫卵呈椭圆形、淡灰色、有卵盖且内含圆形胚细胞，卵黄细胞不充满整个虫卵。对成虫染色观察可见虫体由体壁及内部生殖、消化等系统构成。体壁由皮层和肌层组成，虫体可见生殖系统、消化管和一些肌束与纤维组织，其中生殖系统包括卵巢、子宫和睾丸等生殖器官，消化管分布于整个体腔。虫体核糖体基因ITS-2扩增产物为441 bp，分析显示与GenBank中Explanatum explanatum（AB743577.1）相似性达99.3%。遗传进化分析显示此虫体与Explanatum explanatum具有很近的亲缘关系，同属一个分支。综合剖检病理变化，虫卵特性，虫体形态特性及分子生物学结果，确定该虫体为前后盘科的Explanatum explanatum。本研究结果为前后盘科吸虫分类鉴定提供一定的理论基础，并进一步丰富该科的虫体种类，此外初步了解广西南宁地区水牛前后盘吸虫病的流行情况，并为准确防治吸虫感染提供一定的理论依据。  相似文献   

9.
Immature worms were recovered from the liver parenchyma of rats which received extracts of metacercariae or adult worms of Fasciola gigantica, after challenge infection. When resistance was assessed by counting the number of immature worms, exposure of the animals to extracts of these two stages of the flukes conferred a significant degree of protection against challenge with F gigantica metacercariae. Rats given the extract of metacercariae were more resistant to infection than rats immunised with the extract of adult worms.  相似文献   

10.
Following subcutaneous injection, a proportion of the larvae of Strongyloides papillosus became arrested in the musculature of rabbits and sheep. By the anthelmintic removal of the adult worms from the small intestine, it has been shown in both host species that arrested larvae are capable of continuing their migration and replacing the adult population. While arrested larvae seldom remained longer than 4–5 weeks in the muscles of rabbits, and most migrated earlier, they remained in excess of 12 weeks in sheep. It is suggested that these arrested larvae have the function of maintaining the intestinal population of adult worms.  相似文献   

11.
The effects of the anti-schistosomal drug, niridazole, on the migration of Schistosoma mansoni larvae, biosynthetically radioisotope-labelled with 75[Se]-selenomethionine, was evaluated by autoradiography of compressed tissues of mice treated daily from Days 6 to 10 post-infection with 200 mg kg-1 niridazole. The results were compared with the migration of schistosomula in untreated controls. The distribution of schistosomula was altered in niridazole-treated mice, where there was a delayed migration from the lungs relative to the controls and significantly fewer schistosomula in total appeared to reach the liver. The total percentage of schistosomula detected as autoradiographic foci was significantly lower in treated mice than in the untreated controls. Niridazole-treated mice were free of any foci 10 days after the last treatment and no adult worms were recovered on perfusion of the hepatic portal system relative to control mice from which 5.8% of the infective cercariae were recovered as adult worms at Day 42 post-infection.  相似文献   

12.
To clarify the role of the nutria Myocastor coypus in the epidemiology of domestic fasciolosis in Loire-Atlantique (department of western France), 438 nutrias were trapped in 9 humid areas of the department and 304 nutrias were trapped in 3 farms where Fasciola hepatica was present; all animals were necropsied. Liver flukes were found in 160 nutrias: 38 nutrias randomly taken in the department (8.7%) and 122 trapped in fasciolosis areas (40.1%). The average parasitic burden was 5.7 flukes per nutria. Sixty-five percent of the liver flukes measured more than 18 mm (size of sexual maturity). The coproscopic examinations carried out on 144 infected nutrias showed that 90% of the infected nutrias shed fluke eggs. The hatching rate was 39.6%. Two groups of 100 Lymnaea truncatula snails, originating from 2 different populations, were exposed to F. hepatica miracidiae hatched from eggs collected from infected nutrias. The prevalence of the infection was 74% and 58.6% in the 2 groups of snails. The average redial burden was 6.2 rediae per snail. The total number of metacercariae was 72.4 metacercariae per snail producing cercariae. Two groups of 5 sheep were orally infected by 150 metacercariae of nutria or sheep origin, respectively. The installation rates of F. hepatica in sheep were respectively 31.6% and 29.6% for the two groups. Specific antibody kinetics of sheep were similar whether the metacercariae were of nutria or sheep origin. M. coypus allows the complete development of F. hepatica and releases parasitic elements that are infective for domestic ruminants. Because of its eco-ethologic characteristics, the nutria could be a potential wild reservoir of F. hepatica in France.  相似文献   

13.
This article reviews the actual world FMD situation. In 2000, fifty nine countries officially reported outbreaks of FMD. The disease occurred in Europe (Greece), Asia (Russia, Mongolia, Bangladesh, Cambodia, China, Japan, Laos, Nepal, Pakistan, Philippines, Republic of Korea, Taiwan, Thailand, Vietnam, Iran, Iraq, Turkey, in Caucasian region--Georgia, Azerbaijan and Armenia as well as in Kazakhstan, Kyrgyzstan, Turkmenistan and Tajikistan), Africa (Egypt, Kenya, Mauritania, South Africa, Tanzania, Uganda, Malawi, Namibia, Zambia and Zimbabwe) and in South America (Brazil, Colombia, Uruguay, Bolivia, Peru, Ecuador and Venezuela). In 2001, FMD was still spreading throughout the endemic regions and appeared in some of the west European countries--Great Britain, The Netherlands, France and Ireland. In South America, FMD occurred in Argentina, Uruguay, Brazil and Colombia. In Asia the FMD spread in Turkey, Iran, Afghanistan, Georgia, Azerbaijan, Mongolia, Kuwait, Bahrain, Yemen, Qatar, United Arab Emirates, Oman, Iran, Bhutan, Nepal, Malaysia, Philippines, Thailand and Taiwan. The FMD situation in Africa was unclear, but probably most countries in West, East and South Africa were affected. The most recent data of the OIE from May 2002 confirmed FMD outbreaks in population of pigs in Republic of Korea.  相似文献   

14.
Over a period of one year, from February 1979—February 1980, the abomasa of four dairy cows were examined each week for the presence of parasitic nematodes. Based on the identification of adult male worms, Ostertagia ostertagi (94%) and Trichostrongylus axei (75%) were the most prevalent species, and Haemonchus contortus was absent. Total worm burdens varied from zero (one cow) to 100 890. The geometric mean total number was 3011. The geometric mean number of arrested larval stages was 685. Of the adult worm burden, more than 85% consisted of O. ostertagi, about 12% of T. axei the remaining 3% was other species. No relationship could be found between worm burdens and the age of the cow, the weight of the abomasum or the milk yield.

The adult Ostertagia burden was highest in the period July–September. The numbers and the percentages of arrested larvae were highest in winter, lowest in summer. Besides those of O. ostertagi, small numbers of arrested larvae of T. axei were observed from September onwards. Cows from farms with a zero-grazing system had significantly fewer worms than cows from other farms independently of the time of the year.  相似文献   


15.
During the period from September 1985 to March 1988, the freshwater snails, Semisulcospira libertina, were collected from 4 mountain rivers in Ayama County of Mie Prefecture, which is known as a heavily infected locality with Paragonimus westermani (Kerbert, 1878) Braun, 1899, and were examined for cercariae and rediae of this lung fluke. Of 3,000 snails studied, 80 (2.67%) harbored Paragonimus larvae. The infected snails were found at 3 sites in the Nishitani (A), Nenobi(B), and Higashitani (C) rivers. The infection rate of Paragonimus cercariae at these sites varied from 0.13 to 6.08%. The highest incidence (6.08%) of cercarial infection occurred at site A (Nishitani river), where the prevalence and intensity of infection with P. westermani metacercariae were considerably greater in the 2nd intermediate host crabs. No Paragonimus was observed in 776 snails collected at site D (Taki river), where the incidence and degree of metacercarial infection in crabs were quite small. There was a positive correlation between the infection incidence of P. westermani and the size of S. libertina; the percentage of infected snails increased in larger size classes, reaching 24.14% at a shell length of over 40 mm. In the 80 positive snails there were 51 mixed infections with P. westermani and 1 or 2 other species of trematode larvae. Of these, 43 were double infections and 8 triple. The morphological features of P. westermani cercaria and redia are described.  相似文献   

16.
Seven laboratory mammal and bird species were orally inoculated with 200–1,000 encysted Metagonimus hakubaensis metacercariae that had been isolated from naturally infected lampreys (Lethenteron reissneri) captured in Aomori Prefecture. At 8 and 15 days post-infection, adult flukes were recovered from all of the laboratory animals tested, and therefore, hamster, rat, mouse, dog, cat, chicken and quail were considered as final hosts of M. hakubaensis. Recovery rates of the fluke were higher in dogs and hamsters than in cats, rats, mice, chickens and quails. The flukes recovered from dogs and hamsters showed increased body length and higher fecundity than those recovered from the other hosts. These results indicate that the suitability of dogs and hamsters for M. hakubaensis infection is higher than that of the other laboratory animals.  相似文献   

17.
The present study describes the occurrence of various gastrointestinal helminths, lungworms and liver flukes in Norwegian sheep and goats as assessed from faecal samples and post mortem examinations performed between 2007 and 2010. Faecal samples for gastrointestinal nematode egg counts were collected from 77 sheep flocks and 30 dairy goat flocks from three geographical regions in Norway. Additionally, thirty-two lambs and 16 adult goats were euthanized for necropsy examination and for identification of adult gastrointestinal nematodes and tapeworms, lungworms and liver flukes. The survey showed that there was a higher mean excretion of trichostrongyle eggs in sheep than in goats at the individual level (392 EPG vs. 154 EPG, p < 0.001). For both host species, the mean prevalence and intensity of excreted trichostrongyle eggs were significantly higher in the southern coastal region compared with the inland and northern regions (p < 0.001). Third stage larvae of Trichostrongylus/Teladorsagia, Haemonchus and Nematodirus type were the most prevalent ones in the coprocultures from sheep, whereas larvae of Trichostrongylus/Teladorsagia and Nematodirus type dominated in goats. The most prevalent gastrointestinal nematode species found at necropsy was Teladorsagia circumcincta (75.0 and 81.2% respectively in sheep and goats), while the largest mean worm burdens were recorded for Haemonchus contortus in sheep (724 ± 623) and T. circumcincta in goats (377 ± 529). Other gastrointestinal nematode species were present at low prevalence or in low numbers.  相似文献   

18.
A retrospective study covering a period of 10 years (1990-1999) was carried out using post mortem meat inspection records at the Veterinary Department Headquarters at Kabete to determine the prevalence and economic importance of bovine fasciolosis in Kenya. Meat inspection records from abattoirs in 38 districts distributed over seven out of the eight provinces of Kenya were examined. Prevalence of fasciolosis was calculated as the number of cattle found to be infected with Fasciola, expressed as a percentage of the total number of cattle slaughtered. Using the average weight and market price of a bovine liver, the monetary loss occasioned by condemnation of Fasciola infected livers was calculated. A survey was also carried out at Dagoretti slaughterhouse complex in Nairobi to determine the relative occurrence of F. gigantica and F. hepatica in slaughtered cattle. Cattle slaughtered at Dagoretti slaughterhouse originate from all parts of the country. A total of 5,421,188 cattle were slaughtered in the seven provinces of Kenya during the 10-year period and 427,931 (8%) of these cattle were infected with Fasciola. The region with the highest prevalence of fasciolosis was Western Province (16%) followed, in descending order, by Eastem Province (11%), Nyanza Province (9%), Rift Valley Province (8%), Central Province (6%), Nairobi Province (4%) and Coast Province (3.5%). The total economic loss incurred by the country during the 10-year period as a result of condemnation of the infected livers was approximately US$2.6 million. The total annual economic losses during this period ranged from approximately US$0.2-0.3 million. The highest total economic losses for the 10-year period were recorded in Western Province (US$0.8 million) and Central Province (US$0.7 million). A total of 1584 cattle originating from five provinces of Kenya were slaughtered at Dagoretti slaughterhouse over a period of two months of which 147 (9.3%) were infected with liver flukes. All the liver flukes obtained from the infected livers were identified as F. gigantica. It is concluded that fasciolosis is prevalent in cattle in all provinces of Kenya, that it causes great economic losses as a result of condemnation of infected livers, and that F. gigantica is the main species of liver flukes affecting cattle in Kenya. Local climatic factors, cattle trade, rustling and population numbers, and the presence of the snail intermediate hosts are probably the main factors influencing the incidence of the disease in the various regions of the country.  相似文献   

19.
蛋白质组学是研究一种细胞、组织或完整生物体在特定时空上全部蛋白质及其存在方式的学科。近年来,应用蛋白质组学技术开展了日本血吸虫尾蚴、童虫、成虫蛋白质组,成虫性别差异和排泄分泌物蛋白质组,体被蛋白质组,与药物和诊断相关的蛋白质组等多方面的研究,增加了人们对日本血吸虫的生长发育、免疫逃避等机制的了解,为发掘血吸虫病疫苗、诊断和药物靶点提供了新的线索。  相似文献   

20.
Adult feral swine, naturally infected with kidney worms (Stephanurus dentatus) and gastrointestinal nematodes, were divided into two groups of 10 pigs each. One group was treated with fenbendazole (Panacur, Hoechst AG, Frankfurt am. Main) mixed in feed at the rate of 3 mg kg-1 body weight for 3 days. The second group received feed only and was designated as non-treated controls. The animals in both groups were necropsied 3 weeks post-treatment and examined for the presence of live and dead adult kidney worms in the perirenal and ureteral area, ureteral penetration, the presence of kidney worm larvae in the liver, hepatic scars due to kidney worm larval migration, and for liver fibrosis. No live adult kidney worms were found in the perirenal and ureteral areas of treated pigs, and the non-treated pigs harbored an average of 42.8 live worms. No liver kidney worm larvae were found in the livers of treated pigs, and the non-treated pigs averaged 6.7 live larvae. At necropsy, urine samples from 8 of the 10 treated pigs contained no kidney worm eggs, and only 2 eggs were found in samples from each of the remaining 2 pigs in this group. In contrast, urine samples from 8 of the non-treated pigs contained numerous kidney worm eggs. Reductions in ascarid (Ascaris suum) and nodular worm (Oesophagostomum dentatum) egg counts were also observed in treated pigs.  相似文献   

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