Immunopathogenesis of Ascaridia galli infection in layer chicken

Gastro-intestinal nematode infections in mammals are associated with local T lymphocyte infiltrations, Th2 cytokine induction, and alterations in epithelial cell secretion and absorption. This study demonstrates that Ascaridia (A.) galli infection in chicken also elicits local gut-associated immune reactions and changes in the intestinal electrogenic nutrient transport. In A. galli-infected birds we observed infiltrations of different T cell populations in the intestinal lamina propria and accumulation of CD4+ lymphocytes in the epithelium. The Th2 cytokines IL-4 and IL-13 dominated the intestinal immune reactions following A. galli infection. A. galli-specific systemic IgY antibodies were detected after two weeks post infection, and did only poorly correlate with detected worm numbers. Electrogenic transport of alanin and glucose was impaired in A. galli-infected chicken. Our data provide circumstantial evidence that local immune responses and electro-physiological intestinal functions may be connected and contribute to the elimination of worm infection.

Investigations on the influence of helminth parasites on vaccination of chickens against Newcastle disease virus under village conditions

Prevalence studies have shown that almost 100% of free-range chickens are infected with a wide range of parasites. The infections are mostly subclinical in nature, resulting in production losses and occasionally mortality. Newcastle disease (ND) on the other hand, results in high mortality rates during epidemics. ND is a limiting factor for increasing poultry production in many tropical countries, where frequent reports indicate vaccination failures. The aim of our study was to investigate the influence of helminths on the antibody response after vaccination against Newcastle disease of free-range chickens naturally infected with parasites. Sixty chickens were divided into six groups, of which three were vaccinated against ND with a live De Soto vaccine, while the other three remained non-vaccinated. One group within the vaccinated groups and the one within the non-vaccinated group was kept naturally infected with helminth parasites, while the other two groups in each set were dewormed with fenbendazole and niclosamide, and one of each of these groups was subsequently infected with Ascaridia galli. After vaccination, all the groups were followed for 5 weeks and their antibody titres were determined weekly using a HI test. All the birds were finally challenged 4 weeks after vaccination with a virulent velogenic ND virus obtained from a field outbreak. All the vaccinated chickens seroconverted and had high antibody levels after 3 weeks, but these dropped to low levels at 4 weeks after vaccination. After challenge, the antibody titres rose in the dewormed groups but not in the parasite-infected groups. After 5 weeks, all the parasite-infected animals had significantly lower antibody titres than the dewormed animals. All the vaccinated chickens survived the challenge infection, emphasizing the importance of the cellular immune response. Further studies are needed to examine the effects of the parasitic infection on protection against ND over a longer period.

Effect of different contents of proteins and vitamin B2 in the feed on the prevalence and infection intensity of Ascaridia galli in chickens

A group of 10-day-old chickens was experimentally infected with a dose of 500 infective eggs of Ascaridia galli (Schrank, 1788) (Nematoda). Forty-nine days post infection the chickens were necropsied and the infection intensity and prevalence were determined. The group maintained on the feed containing 11% of protein showed higher infection intensity and prevalence compared to the chickens fed a diet containing 19% of protein. The addition of vitamin B2 to the feed containing 11% protein resulted in lower intensity and prevalence of the infection. In both series of experiments no effect of Zn-bacitracin or vitamin B2 on infection intensity or prevalence was observed for chickens fed feed containing 19% of protein.

Cerebral larva migrans in a raccoon (Procyon lotor)

During 1997, gross and histopathologic examinations were performed on an adult female raccoon (Procyon lotor) that was live-trapped in Corvallis, Oregon. Multifocal eosinophilic granulomas indicative of neural and visceral larva migrans were observed. However, within these granulomas, the presence of parasitic larva was seen only in the cerebrum. Morphologic characteristics indicated that the nematode was an ascarid larva. However, it was smaller than the larva of Baylisascaris sp. This appears to be the first documented case of cerebral larva migrans in a raccoon.

[Data on the biological cycle of the ascaridoid Ophidascaris trichuriformis, parasite of snakes]

Ophidascaris trichuriformis is an ascaridoid commonly found in some species of Colubridae snakes. Similarly to what has been observed with several ascaridoid species, in O. trichuriformis the larvae, when still inside the egg-shells, reach the 3th snake stage around the 8th day of incubation in cultures kept at around 25 degrees C. Tentative assays to infect mice, snakes, toads, fish, and tadpoles of Hyla fuscovaria and Bufo sp. was made through the administration of embryonated eggs. Eggs didn't even eclode in mice, snakes or toads in such experiments; while in fish, although the eggs ecloded, its larvae were eliminated after the 4th day. In H. fuscovaria and Bufo sp. tadpoles, larvae were liberated from egg-shells and their development was observed up to the 36th day. They grew from the 6th hour to the above mentioned day, after which larvae were longer in Bufo sp. than in H. fuscovaria. By the 36th day distinction of sexes was possible through examination of genital primordia whose morphology and location differed in male and female larvae. From the 30th day on, following the recognizable beginning of metamorphosis in anuran amphibians and going up to the 65th day after experimental infection, an intense growth of the larvae infecting Bufo sp. was observed; the growth of such larvae was negligible between the 65th and the 85th days. Five snakes (Waglerophis merremii) were given per os larvae obtained from Bufo sp. after the 65th day of infection; these snakes died on the 53th, 54th, 60th, 110th and 116th days after their own infection, respectively, and in each of then 4th stage O. trichuriformis larvae were found in the stomach. The gastric location of such larvae in each snake was identical to the one in which adult worms of this same species are regularly found in natural infections: all of them had the middle part of the body embedded into the stomach wall while both anterior and posterior extremities kept free towards the lumen of the organ.

[Effect of the pH of Ascaridia galli egg culture medium on the experimental infection in chickens]

1. A prolonged preservation of Ascaridia galli eggs in acid medium when cultivating them under laboratory conditions inhibits considerably the establishment of Ascaridia galli in the organism of chickens. The neutralization of medium of egg cultivation 3 days before their application for infesting facilitates the increase of larvae established in the organism. 2. In chickens invaded with Ascaridia galli eggs cultivated in medium with pH 8.0, larvae develop in the period of 7--21 days of invasion in the amount of 2.5--69 times more than in chickens receiving the same eggs but which have been cultivated in acid medium (pH 2.2) for the whole cultivation period. 3. With the increase in invasion period, the number of established larvae decreases in both test groups, but in chickens receiving eggs which have been cultivated in medium with pH 8.0, the number of larvae is considerably higher.

Weight changes in chickens placed on different levels of nutrition and varying degrees of repeated dosage with Ascaridia galli eggs

The effect of continuing ingestion of eggs of A. galli on growth rates of chickens placed on different nutritional levels was studied under repeated doses of 10, 100 and 1000 infective eggs/day. With increasing amounts of protein in feed, there occurred significant weight differences between infected groups, the highest protein levels showing the longest duration in weight depression due to infection. On the other hand, assuming adequate nutrition of host, highest effects on growth rates were seen in chickens receiving daily doses of 1000 eggs daily and the lowest in chickens receiving 10 eggs daily.

The effect of repeated dose on growth rate is similar to the effect of single infections reported by previous workers except that the duration of the growth depression was much longer in the former due to pathogenic effects of inhibited larvae.

The author is indebted to the Department of Technical Cooperation, under whose Fellowship this study was carried out; to the Department of Zoology, Edinburgh University, where the work was done; to the Ministry of Agriculture, Fisheries and Food; Poultry Research Laboratories, Lasswade, for the free supply of chickens used here; and finally to Dr J. A. Campbell of Edinburgh University for his keen interest and advice throughout this work.

Observations on the pathogenicity and pathology of Ascaridia galli

The pathogenicity and pathology of Ascaridia galli infections of poultry were studied using repeated doses of varying numbers of eggs. No significant effect due to infection was seen on p.c.v. and Hb. values of infected chickens. Haemo concentration occurred parallel with sporadic diarrhoea, which follows high levels of repeated dosing. This phenomenon complicated the interpretation of blood protein values. A/G ratios were, however, worked out and analysed. No significant differences were noticed between the groups and it was concluded that under the levels of inoculation employed during the study there were no significant effects of A. galli infections on blood protein values as well as p.c.v. and Hb.values of infected chickens.

Symptomatic developments, macroscopic lesions and pathological changes of intestinal tissues due to infection were followed up in detail. They were most severe in chickens on the least nutritive diet and sustaining the highest levels of repeated doses. Pathogenicity of larval and adult parasites was described. The presence of large numbers of adult parasites was associated with intestinal obstruction in host. This was seen mostly in chickens on low nutrition and sustaining either low or high levels of repeated inoculation, and very rarely also in chickens under high plane of nutrition but sustaining repeated inoculation of small numbers of eggs. Cellular infiltration as a result of infection was found to be extremely rare.It was present as fibroblasts and only in association with dead larvae.

The author is indebted to the Department of Technical Cooperation, under whose Fellowship the study was carried out; the Department of Zoology, Edinburgh University, for facilities provided; the Ministry of Agriculture, Fisheries and Food; Lasswode Poultry Research Laboratories, for the free supply of chickens used here; Dr J. A. Campbell of Edinburgh University for his keen interest, encouragement and advice throughout this work; and finally to G. Obiwelozor for reproducing the photographs from the original manuscript.