Abstract Intestinal helminths may cause minimal gastro-intestinal symptoms but many (e.g. Ascaris) have a major impact on human health compromising the nutritional status of children in developing countries (see Chapter 1) Several species of nematodes, trematodes, and cestodes live in the human intestine and produce eggs which are passed in the faeces. Eggs of lung and liver flukes also are passed in the faeces. Parasitological diagnosis of most intestinal helminthic infections depends on finding and identifying these eggs. With the Taenia species, however, it is rare to find eggs in faeces as the proglottids are usually passed whole. Similarly, Enterobius vermicularis deposits its eggs on the perianal skin and eggs are seldom found in the faeces. Strongyloides stercoralis produces first stage larvae (L1) instead of eggs.

Jirds were vaccinated by three to five subcutaneous (SC) injections of infective larvae ofBrugia pahangiwhich had been irradiated at 25, 45 or 90 krads from a60Co source. They were challenged either SC or intraperitoneally. Vaccination with four doses of 50 larvae irradiated with 25 krads produced 49·3% resistance to IP challenge worms and 39·8% against SC challenge worms. Five doses of larvae irradiated with 45 krads produced 62% resistance to SC challenge. Three doses of larvae irradiated with 90 krads produced 74·9% resistance to SC challenge and five doses produced 76·2% resistance. The reasons why irradiated larvae produce resistance whereas normal larvae do not are discussed.

The mortality of Aedes aegypti mosquitoes increased; immediately following a blood meal containing microfilariae of Brugia pahangi, when infective larvae began to migrate out of the flight muscles and when infective larvae were lost from the mosquitoes during a blood meal. When infective mosquitoes took a second blood meal 86.2% of the infective larvae escaped from their bodies. However, only 50.3% escaped when mosquitoes fed through a thin layer of cotton. Infective larvae in the abdomen of the mosquitoes stood the least chance of escaping from the insects. When infective mosquitoes were offered a third blood meal four days later, the proportion of infective larvae in the head and labium had risen from 56.6% in the control group to 66.0% and 69.4% in the two test groups. At this third feed 54.7% and 75.7% of the infective larvae were lost from mosquitoes with a low and medium pre-feeding worm burden respectively. This suggests that the escape of infective larvae from mosquitoes with only a few worms is less efficient than from mosquitoes with a medium worm burden.

Jirds were vaccinated by three to five subcutaneous (SC) injections of infective larvae of Brugia pahangi which had been irradiated at 25, 45 or 90 krads from a 60Co source. They were challenged either SC or intraperitoneally. Vaccination with four doses of 50 larvae irradiated with 25 krads produced 49.3% resistance to IP challenge worms and 39.8% against SC challenge worms. Five doses of larvae irradiated with 45 krads produced 62% resistance to SC challenge. Three doses of larvae irradiated with 90 krads produced 74.9% resistance to SC challenge and five doses produced 76.2% resistance. The reasons why irradiated larvae produce resistance whereas normal larvae do not are discussed.

Filarial infections commonly involve chronic tissue responses to these complex and resiliant organisms. These responses, which occur with a number of the parasitic stages of filariae, involve macrophages, and these cells appear to be important in immunologically induced destruction and removal of these important parasites of man and animals. Details of their presence and experimental induction as well as their distinction into a number of morphological types, including multinuclear (giant cell) forms, is described in this communication. The ability of these various forms to function in phagocytic and immunologically mediated adherance assays is also described.

The clinical and autopsy findings of a two and a half year-old infant with Toxocara sp. infection of the brain and granulomatous lesions in the liver are reported. The cause of death was non-accidental injury. The relationship between Toxocara infection and behavioural disorders is discussed.

Journal Article Techniques for concentration and identification of microfilariae from peripheral blood Get access D.A. Denham D.A. Denham Dept. of Medical Helminthology, London School of Hygiene and Tropical Medicine, Keppel St., London WC1E 7HT UK Search for other works by this author on: Oxford Academic PubMed Google Scholar Transactions of The Royal Society of Tropical Medicine and Hygiene, Volume 76, Issue 1, 1982, Page 132, https://doi.org/10.1016/0035-9203(82)90040-2 Published: 01 January 1982 Article history Accepted: 16 August 1981 Published: 01 January 1982

Journal Article Techniques for concentration and identification of microfilariae from peripheral blood Get access D.A. Denham D.A. Denham Dept. of Medical Helminthology, London School of Hygiene and Tropical Medicine, Keppel St., London WC1E 7HT UK Search for other works by this author on: Oxford Academic PubMed Google Scholar Transactions of The Royal Society of Tropical Medicine and Hygiene, Volume 76, Issue 1, 1982, Page 132, https://doi.org/10.1016/0035-9203(82)90040-2 Published: 01 January 1982 Article history Accepted: 16 August 1981 Published: 01 January 1982

Feline eosinophils and neutrophils readily adhered in vitro to the sheaths of microfilariae of Brugia pahangi in the presence of suitable serum. Both cell types flattened along the surface of the parasite undergoing cytoplasmic changes which included degranulation. Adherence was dependent on properties of both the serum and the history of the microfilaria used. Two types of serum factor were found to mediate adherence. Heat labile factors were present in sera from infected and uninfected cats as well as in sera from other species. They were removed by preincubation of sera with zymosan suggesting that complement components were involved. This suggestion was supported by the demonstration of C3 on the surface of microfilariae participating in adherence reactions. A heat stable factor, present in the serum of less than 10% of infected cats, also mediated adherence. This factor was demonstrated to be IgG by immunoadsorption and immunofluorescence. The ability of the microfilariae to participate in the adherence reaction mediated by complement factor varied with maturation of the parasite. Microfilariae obtained directly from the uteri of adult worms, or produced in vitro, did not possess the ability to participate in adherence. Young blood microfilariae (i.e. taken from the blood of cats recently patent) were similar to the in vitro produced parasites; however, the majority of blood microfilariae from infections of greater than three weeks patency participated in this form of adherence. No difference between blood and uterine/in vitro microfilariae was seen in adherence reactions mediated by heat stable antibody.

Cats were vaccinated by the inoculation on 10 occasions of approximately 300 larvae of Brugia pahangi which had been irradiated with 10 krad cobalt 60. They were challenged on 3 occasions with normal larvae of either B. pahangior B. patei. The vaccinated cats were resistant to challenge as demonstrated by either longer pre-patent periods or failure to become microfilaraemic and by having fewer third, fourth or adult worms than normal controls. Although the vaccination procedure was unpractically heavy these results lend encouragement to the possibility of developing vaccines against filarial infections.

A variety of techniques have been used to detect damage to lymphatics in man and animals and some of these can be used in the study of cats or dogs infected with Brttgia pahangi. Dissection at autopsy or under anaesthesia after the injection of Evan*s Blue is, perhaps, a perfect technique for determining gross pathological change and also allows histopathological studies to be undertaken, but being a once and for all system does not permit chronological studies. visualizes lymphatics using Lipiodol

AbstractThe structure of the cuticle of third and fourth stage larvae and of adultBrugia pahangi(Nematoda: Filarioidea) was studied by light microscopy and by transmission and scanning electron microscopy. The cuticle of these worms was basically typical of the class Nematoda and consisted of cortical, matrix, and basal layers. Finely spaced annulation grooves were present and their function is discussed.Descriptions of the cuticular ultrastructure of filarial nematodes are meagre. Studies on the cuticle of adult worms are limited to those of Kagei (1960, 1963) onSetaria cerviandLitomosoides cariniiand of McLaren and Hockley (personal communication) who examinedL. carinii and Dipetalonema vitea