The pre-feeding and feeding periods of larvae, nymphs and adults of Rhipicephalus appendiculatus on rabbits (Oryctolagus cuniculus) were investigated. Larvae and nymphs required at least 8–9 days after hatching and moulting respectively before they could attach and start feeding, while adults required at least 6–9 days. But longer periods of starvation improved the proportion of ticks that successfully fed.

After attachment, there was always an initial period of slow feeding, which was followed by a phase of very rapid feeding before the engorged ticks detached from the host. Larvae detached 4–5 days after attachment, nymphs detached after 5–6 days and adults detached 7–9 days after attachment.

Lambs which were given 60000 infective larvae ofNematodirus battus progressively threw off adult nematodes from day 20 onwards. Large, hexagonal crystals appeared in the intestine of the adult nematode at about this time and caused blockage of the intestinal-rectal or -cloacal junction. Lambs which were given 1000–2000 infective larvae did not throw off the infection, and adult nematodes from lambs which had been infected for up to 74 days did not contain these crystals. Chemical, histo-chemical and X-ray microanalysis tests on the crystals indicated that they are lipoprotein in composition. The crystals arise within the lumen of the nematode and appear to be associated with the development of immunity to this nematode in lambs.

Groups of mice were infected with 1,5 or 10 cysticercoids of Hymenolepis microstoma. Infections were terminated with the anthelmintic ‘Zanil’ after 5, 15 or 30 days and the mice challenged with 6 cysticercoids. The growth of the worms in the secondary infections decreased as either the intensity (number of cysticercoids administered) or duration of the primary infections increased. It is postulated that the results have an immunological basis.

The effects of complement and/or specific antibodies on the larval and adult stages of Echinococcus granulosus were studied in vitro. Lysis and death of both protoscoleces and adult E. granulosus occurred within 10 min to 24 h in 50% fresh normal sera used as a source of complement, without the presence of specific antibodies. The lytic and lethal reaction was marked in fresh sera from guinea-pigs, calves, dogs, man and sheep, but only slight in fresh sera from English rabbits and horses. Guinea-pig sera were shown to be complement deficient after reacting with worms and all reactions were abolished after sera had been heated to 56 °C for 30 min. Fluorescent antibody studies failed to detect host antibodies at the parasite tegument. It is suggested that activation of the complement system occurs via the alternate pathway, that it acts independently of the immune system and that it is lethal to a wide range of cestode parasites.

In contrast, marked agglutination/precipitation reactions with protoscoleces and precipitation reactions with adult E. granulosus were observed after incubation in heat inactivated 50% canine antisera, but not in normal sera. The antigen-antibody nature of these reactions was established by fluorescent antibody studies and the areas of antibody attack pinpointed. In spite of these reactions, worms remained healthy and active over a period of 8 days.

Egg production by Reighardia sternae, implanted at various stages of maturity into the interclavicular air sacs of captive gulls, is described.

Females produce only 2900 eggs per lifetime over a short patent period of 1–3 days. The problem of a direct life-cycle in relation to this unusually low fecundity is discussed, and speculation is advanced concerning a possible parasitic behavioural trait which could facilitate direct transmission. The hazards of the latter are also offset by auto-reinfection.

Sporulation rates of normal oocysts and oocysts isolated from lambs infected with coccidia and fed Aureo-S-700R for 25 days were studied at different temperatures. The viability and infectivity of the latter were also investigated.

Temperatures of 5 and 10 °C inhibited sporulation of oocysts, but when the same oocysts were subsequently incubated at 25 °C, they sporulated. At 35 and 40 °C, sporulation was initially fast, but death and degeneration of oocysts occurred at these temperatures after 3 days.

Normal oocysts sporulated faster and in greater numbers than oocysts isolated from medicated lambs; both kinds of oocysts sporulated best between 20 and 25 °C.

Lambs inoculated with oocysts from medicated lambs passed fewer oocysts for a shorter period of time than lambs inoculated with normal oocysts. The former lambs gained more weight, passed better formed faeces, ate better and had higher PCV and haemoglobin values than the latter.

Male and female congenitally athymic nude (nu/nu) mice infected with a single cysticercoid of Hymenolepis diminuta at 6 weeks of age retain the infection for at least 33 days. In the males of their phenotypically normal litter-mates, however, a single cysticercoid infection establishes and grows but is expelled between days 11 and 17. The unresponsiveness of the nude mouse to single H. diminuta infection is evidence that the immune rejection from normal mice is thymus-dependent.

The main components of the schistosome tegument were found to be neutral glycoprotein and phospholipid; a small quantity of glycolipid was observed in the male dorsal tegument. The tegument can be differentiated from other schistosome tissues on the basis of enzyme content; three hydrolytic enzymes were shown to be specifically localized in the tegument: alkaline phosphatase, adenosine triphosphatase and indoxyl esterase. It is suggested that these enzymes could be used as intrinsic markers for tegument structures. The subtegumental cells appear to be the major sites of biosynthetic activity since they contain large amounts of RNA and mitochondrial enzymes.

Oocysts of the Weybridge and Houghton strains of Eimeria maxima and a fresh field isolate were similar and measured on average 30·9 × 22·4 μm. The Weybridge strain and the field isolate produced similar pathogenic effects in 6-week-old chickens, high doses causing 50–80% mortality and severe weight loss. The Houghton strain was slightly less pathogenic and few birds died but more oocysts were produced. With each strain, a single dose gave complete immunity to a light challenge with the homologous strain. Two or 3 immunizing doses gave complete immunity to a heavy homologous challenge but were not sufficient to protect against heterologous challenge.

The numbers of mature worms which developed in young rats after their mothers were injected with 4000 L3 late in lactation were 1% (Nippostrongylus brasiliensis) and 24% (Strongyloides ratti) of the dose administered. The low value for N. brasiliensis validates the conclusion that milk is a real and important vehicle for infection in S. ratti since possible errors from skin invasion of the young would have been common to both species.

The level of mature S. ratti infection in lactating mothers in this experiment was negligible, 97–99% of the adult worms appearing in the offspring.

These results may indicate that the milk route is possible with N. brasiliensis even though it is quantitatively insignificant.

Eimeria marsica Restani 1971 is re-described from oocysts recovered in pure culture from experimentally infected coccidia-free lambs. The ellipsoidal oocysts, which measure 19·1 × 13·1 μm, possess an inconspicuous micropylar cap. The prepatent period varies from 14–16 days. E. marsica is recorded for the first time from sheep in England.

Chicks were given daily inoculations of 1 or 5 oocysts of Eimeria maxima or 5 or 20 oocysts of E. acervulina.

The inoculations ceased after 20 days with E. maxima or 25 days with E. acervulina when oocyst production had stopped. The responses to subsequent heavy challenges showed that with both species the immunity arising from the serial inoculations was stronger and/or more enduring than that produced by single inoculations of comparable numbers of oocysts.