Immune responses of swine to oral inoculation with embryonated eggs of Ascaris suum

Responses of swine to oral inoculation with embryonated eggs of Ascaris suum were monitored, using lymphocyte blastogenesis assays, indirect radioimmunoassays, and peripheral eosinophil counts (EC). Transient cell-mediated immune responses of peripheral lymphocytes were detected by lymphocyte blastogenesis assay as early as postinoculation day (PID) 2, but were rarely positive for consecutive samples taken at 2-day intervals. Humoral antibodies were first detected at PID 6 to 17 by indirect radioimmunoassays in the various experiments. Positive cutaneous delayed hypersensitivity reactions were observed when pigs were tested at 6 to 7 weeks after inoculation. Histopathologic examination verified infiltration of lymphocytes into the lesions. The EC increased as early as PID 4 to 7 and showed a secondary increase after the 2nd oral inoculation of eggs to as high as 11,400/mm3 (44% of the total WBC). Subsequently, EC decreased rapidly 14 days after the last inoculation of eggs.     

苏云金芽胞杆菌伴胞晶体蛋白对猪体内蛔虫的作用及其血液生理生化指标的分析

感染性猪蛔虫卵以每头份3000个卵的量感染断奶仔猪，于第3天开始肌肉注射不同剂量苏云金芽胞杆菌晶体蛋白（insecticidal crystal proteins，ICPs），每天1次，连续4d。同时测定猪血液生理生化指标，饲喂2个月后收集猪粪便计算虫卵数。结果显示，感染猪出现咳嗽、发热等临床症状，GOT、GPT、ALP、LDH等指标明显升高，经ICPs治疗后又恢复正常。粪便检查，ICPs高剂量组（16．08mg）的EPG（每克粪便虫卵数）为0，而ICPs低剂量组（9．45mg）的EPG为394，未经ICPs作用对照组EPG为2113，差异极显著（P〈0．01），证明ICPs对猪体内猪蛔虫具有较好的杀灭作用。     

猪蛔虫研究进展

猪蛔虫病是仔猪常见的多发性寄生虫病 ,可导致仔猪的腹泻、消瘦、贫血、出血、生长不良 ,并易引起其它疾病的继发 ,严重的导致仔猪死亡。本病流行和分布极为广泛 ,对我国养猪业造成的损失较为严重。其病原体为寄生于猪小肠中的蛔科 (Ascaridae)大型线虫。猪蛔虫属专性寄生 ,它既不寄生于马属动物 ,也不寄生于反刍动物。有时猪蛔虫可能误入非专性宿主体内 ,但不能发育为成虫。本文就近年来国内外猪蛔虫的研究进展作一综述。目前 ,人们对猪蛔虫的研究主要集中在以下几个方面 :1　蛔虫的呼吸机制和代谢这是猪蛔虫研究的热点。 Kita等 [1] 研究…     

Protective immunity to Ascaris suum: analysis of swine peripheral blood cell subsets using monoclonal antibodies and flow cytometry

Outbred domestic swine or SLA inbred miniature swine were exposed to Ascaris suum either naturally on contaminated lots or by inoculation with UV-irradiated attenuated eggs. Both inbred and outbred swine developed virtually complete protection to a challenge of 10 000 eggs after natural exposure, but inbred swine were less resistant than outbred swine after UV-egg exposure. Flow cytometric analysis of peripheral blood mononuclear cells from these animals, performed to determine changes in cell subsets including helper T-cells, cytotoxic/suppressor T-cells, macrophages, and cells expressing class II major histocompatibility antigens, showed that both outbred and inbred swine had similar responses after parasite exposure. The levels of helper T-cells and cytotoxic/suppressor T-cells did not change after parasite exposure, while there was an appreciable but transient increase in macrophages only in those swine naturally exposed to A. suum. Swine exposed to A. suum, both naturally and by inoculation with UV-eggs, showed an increase in the amount of class II antigens detectable per cell. In a second set of experiments, outbred swine were exposed to A. suum naturally or by repeated experimental inoculation with different doses of normal eggs, and protective immunity and changes in blood cell subsets were determined. The greatest change in blood cell subsets was found at 3 and 5 weeks after initial parasite exposure, when macrophages were elevated moderately in a group of pigs inoculated every other day with 1000 eggs and markedly in a group that was naturally exposed; class II antigen expression was also increased during this period. These increases preceded peak serum antibody responses, which were lower in the naturally-exposed group relative to the experimentally-inoculated group. Both groups had high levels of protective immunity. This suggests than natural exposure to A. suum may activate cells and enhance specific immune responses to give high levels of protection.     

苦楝皮乙醇提取物驱除猪蛔虫效果研究及对猪主要免疫指标的影响

进一步考察苦楝皮的驱虫效果和毒副作用。用云南苦楝皮乙醇提取物,对人工感染猪蛔虫的猪只进行不同药物浓度组与空白组的药效对比试验,并在用药前后对猪只进行免疫指标的检测。结果表明,苦楝皮乙醇提取物的高、中浓度对治疗猪蛔虫病的效果较好,驱虫率分别达到87．2％和79．5％,虫卵减少率分别为87．3％和80．2％,与对照组相比差异极显著;对各项指标的检测表明,苦楝皮提取物能提高猪的非特异性免疫机能,在治疗剂量内使用安全。     

Reinfection of Yearling Calves with Ascaris suum

Naturally occuring outbreaks of Ascaris suum infection in calves have usually beeen found in animals nine to 12 months of age. The circumstances surrounding these outbreaks suggest that yearling calves are either particularly susceptible to a primary exposure to A. suum or react strongly to A. summ after sensitization early in life to this or some related ascarid. To determine the effect of reinfection with A. suum nine to 12 months after varying levels of exposure to this nematode, six calves were inoculated with 200,000 to 9,000,000 eggs. Neither death nor, in general, severe clinical signs resulted from reinfection. All calves were examined 15 days after reinfection with pathological changes noted only in the lungs and consisting of emphysema, alveolar wall thickening as well as accumulations of fibrin, eosinophils and hemorrhage in the lumina of alveoli. The findings suggested that exposure to A. suum early in life is not a factor in the development of disease in calves infected at one year of age. It was also found that the eosinophilia that develops following a primary infection with A. suum evidently persists for at least one year.     

Temperature and metal ions-dependent activity of the family I inorganic pyrophosphatase from the swine roundworm Ascaris suum

Temperature dependence, heat stability and metal ions-dependent activity were examined on the Family I inorganic pyrophosphatase (PPase) recently identified from Ascaris suum. Recombinant A. suum PPase (rAsPPase) showed an optimal activity at 55 degrees C. The rAsPPase was heat stable at 40 degrees C in the absence of added Mg(2+) and at 50 degrees C in its presence. The enzyme required divalent metal ions for its activity. The preferences for the metal ions (5 mM concentration) were in the order: Mg(2+)> Co(2+)> Cu(2+)> Fe(2+)> Zn(2+)> Mn(2+). On the contrary, enzyme activity was inhibited by Ca(2+). These findings suggest that catalytic features of AsPPase are consistent with the Family I PPases reported from a wide range of organisms.     

Mature Ascaris suum in naturally infected calves

In two small farms in Sweden young calves were found to be naturally infected with Ascaris suum. One of the calves expelled mature worms with the faeces, one had a great number of worms in the ductus choledochus and two others had worms in the intestine. Most of the worms were mature and at the egg-producing stage. The morphology of the eggs and the adult worms indicated that these parasites were A. suum and that Toxocara (syn. Neoascaris) vitulorum could be excluded.     

The development of Ascaris suum in calves.

To determine the development of Ascaris suum after a primary and a secondary infection, 18 calves were inoculated with 2,000,000 infective eggs and examined from 18 hours to 13 days postinfection. At 18 hours larvae were recovered from the wall of the abomasum, duodenum and jejunum. They were found in small intestine lymph nodes on the third day, in the liver at five days and were most abundant in the lungs on days 7 and 9. The pattern of recovery of larvae from the lung between days 5 and 13 postinfection was similar after a primary or a secondary infection. Slower growth of larvae following a secondary infection was the only evidence of resistance to A. suum. There were no pathological changes observed in the alimentary canal. White foci were found on the surface of the liver as early as the third day. The rapid decline in the number of A. suum in the lungs after the ninth day was considered to be related to immobilization or death of larvae soon after the reaction to them commences.     

Seminal vesicle growth induced by Ascaris suum infection

This study was designed to determine the effect of Ascaris suum infection upon growth of mouse vesicular glands. Mice were infected with varying dosages of A. suum eggs and killed after six weeks. Results indicated a dose dependent increase in seminal vesicle weight, independent of total body weight.     

Ascaris suum Infection in Calves III. Pathology

Gross changes in the lungs of Ascaris suum- infected calves consisted of atelectasis and hemorrhagic foci, edema and emphysema, frequently with bullae. Prominent microscopic lung lesions were edema and emphysema of the interlobular septa with large numbers of eosinophils within and around lymphatics, peribronchiolar lymphoid nodules and parasitic granulomas. Many of the microscopic features were consistent with those found in atypical interstitial pneumonia. Changes in the alveoli were atelectasis, the exudation of plasma proteins, mononuclear cells and eosinophils, and alveolar wall thickening. Lesions found later included fibrosis and fetalization of the alveolar walls. Plasma cells and neutrophils were not common. Challenge with Toxocara canis after sensitization with A. suum resulted in the lungs developing a few areas of atelectasis. Migration of T. canis to lungs of calves is slower than A. suum. A. suum larvae were always found in bronchi, bronchioles and alveoli of calves that died. Lesions were observed in the liver but not the kidney of A. suum infected calves; both lung and liver lesions tended to resolve with time.     

Ecological influences on transmission rates of Ascaris suum to pigs on pastures

A study was conducted to determine the distribution and transmission rate of Ascaris suum eggs and Oesophagostomum dentatum larvae in a pasture/pig house facility, which during the preceding summer was contaminated with helminth eggs by infected pigs. In May, four groups of 10 helminth na?ve tracer pigs were exposed to fenced sections of the facility for 7 days and necropsied for parasite recovery 9-10 days later (trial 1). The highest rate of A. suum transmission (201 eggs per day) occurred in the pig house (A). On the pasture, egg transmission decreased with the distance from the house: 8 eggs per day in the feeding/dunging area (B); 1 egg per day on the nearest pasture (C); <1 egg per day on the distant pasture (D). Only a few O. dentatum infections were detected, indicating a poor ability of the infective larvae to overwinter. Soil analyses revealed that the highest percentage (5.8%) of embryonated A. suum eggs were in the house (A). Subsequently, the facility was recontaminated with A. suum eggs by infected pigs. A replicate trial 2 was conducted in the following May. A major finding was the complete reversal of egg distribution between the 2 years (trials 1 and 2). In contrast to previous results, the highest rates of transmission (569 and 480 eggs per day) occurred in pasture sections C and D, and the lowest transmission rates (192 and 64 eggs per day) were associated with the feeding/dunging sections and the house (B and A). Soil analyses again supported the tracer pig results, as the pasture sections had the highest concentrations of embryonated eggs. Detailed soil analysis also revealed a non-random, aggregated egg distribution pattern. The different results of the two trials may be due to the seasonal timing of egg deposition and tracer pig exposure. Many eggs deposited during the summer prior to trial 1 may have died rapidly due to high temperatures and dessication, especially when they were not protected by the house, while deposition in the autumn may have favored egg survival through lower temperatures, more moisture, and greater sequestration of eggs in the soil by rain and earthworms. The latter eggs may, however, not have become embryonated until turnout the next year. The results demonstrate that yearly rotations may not be sufficient in the control of parasites with long-lived eggs, such as A. suum, and that a pasture rotation scheme must include all areas, including housing.     

Ascaris suum antigens incorporated into liposomes used to stimulate protection to migrating larvae

Four- to 8-week-old SPF pigs were immunized, using antigens of Ascaris suum incorporated into liposomes, via intestinal cannula or orally. Avridine was also incorporated in the liposomes in one experiment and interleukin-2 (IL-2) injected into pigs in another experiment. A priming dose of embryonate eggs (80-470 eggs/pig) were given in four of six experiments. Compared to control animals, the greatest protection of pigs to migrating ascarid larvae from a challenge dose of 10,000 embryonated eggs occurred where pigs received (1) a priming dose of eggs plus second-stage ascarid larval wall incorporated into liposomes, with or without avridine or IL-2, or (2) a priming dose of eggs plus ascarid intestinal aminopeptidase incorporated into liposomes with IL-2. The degree of protection was not statistically significant due, in part, to the variability in the responses of animals in the same treatment groups and the small number of animals per group. In general, only low titers of specific serum antibodies were detected and specific antibodies were not detected in the intestinal washing.