Scanning electron microscope observations of the frontal papillae and peribuccal cuticle of four species of raillietiellid pentastomids have shown an array of sensilla which are grouped in characteristic patterns. The arrangement of sensilla is remarkably uniform within the species studied and it cannot be used in specific diagnosis. Possible functions are suggested.

Orgyia leucostigma haemocytes were able to encapsulate and destroy eggs of Hyposoter species, thereby preventing successful parasitism. When host larvae had previously been parasitized by Cotesia melanoscela, however, this response was not observed, and 3 different Hyposoter species could be reared to maturity in the normally non-permissive host. Appropriate injection experiments established that C. melanoscela virus and venom were both required in order for successful parasitism by Hyposoter to occur. Covalent cross-linking of C. melanoscela viral DNA led to an immune response against Hyposoter larvae, but not eggs, suggesting that an active viral genome may be required for complete development of Hyposoter species in tussock moth larvae.

A new subgenus and species of avian haemocytozoon Fallisia (Plasmodioides) neotropicalis is described. The principal characteristics are the main host cells, thrombocytes and mononuclear leucocytes, where trophozoites, schizonts and gametocytes are found. Occasionally, granulocytes and very rarely reticulocytes are also parasitized. Phanerozoites very similar to those of Plasmodium of birds are also present. The host is the domestic pigeon, Columbalivia, an imported species but similar parasites have been identified, always mixed with species of Plasmodium, in several indigenous species of Ciconiiformes, which seem to be the natural hosts. This is the first report in birds of a representative of the genus Fallisia, parasites of neotropical lizards.

Human fibronectin isolated from citrated blood was tested for its ability to bind to Plasmodium falciparum by an indirect immunofluorescent assay using rabbit antiserum to human fibronectin. A positive reaction was observed on merozoites inside schizont-infected erythrocytes. The binding was not observed on non-parasitized red blood cells. The effect of human fibronectin on P.falciparum growth was further studied using an in vitro inhibition assay; 50% inhibition of parasite multiplication was obtained with approximately 100 μg/ml of human fibronectin. Slight inhibition was observed below 10 μg/ml. The significance of this finding is discussed.

The transmission mechanisms of microsporidia between generations of Operophtera brumata, a geometrid moth with an univoltine life-cycle, have been investigated. The parasites, Orthosoma operophterae, Pleistophora operophterae and Nosema wistmansi were present in moths collected from Wistman's Wood on Dartmoor. An infection rate of 100% was found in eggs laid by moderately or heavily infected female moths. Thus, 100% infection was found in eggs laid by 78 out of 90 infected females. Lower prevalences were found in eggs laid by the remaining 12 and these moths were subsequently shown to have very light infections. Male moths do not pass on this infection to progeny. The development of O. operophterae was followed during embryonation. The microsporidia do not invade the cells of the developing larva but are restricted to the yolk, where spores accumulate in abundance after earlier merogonies. When the larva is mature and ready to hatch, spores are ingested with the remains of the yolk, as the larva eats its way through the egg-shell. Spores are then found in the meconium in the lumen of the gut. These spores are infective and, once the gut of the larva has become functional, are responsible for infecting the tissues of the larvae which harbour them, as well as healthy larvae reared with them. Spores of O. operophterae held in the natural environment for 7 months from winter until mid-summer still retained infectivity and those contaminating the environment from the bodies of one generation must contribute to transmission between generations.

This study was based on the experimental exposure of beetles to homologous and heterologous infections of Hymenolepis diminuta and Raillietina cesticillus. The results demonstrated that, for both species over the range of parasite densities employed, the presence of a primary infection had no effect on the establishment success of an homologous challenge infection. The establishment success of R. cesticillus cysticercoids was not affected by the presence of an H. diminuta infection. The existence of an R. cesticillus infection, however, severely reduced the establishment success of an H. diminuta infection. The reduction in H. diminuta establishment was greatest in R. cesticillus infections less than 10 days old. The plausibility of some of the mechanisms that are potentially responsible for the reduction in H. diminuta establishment success is discussed, as is the possible ecological significance of these results.

The biochemical characteristics of phenol oxidase obtained from Penetrocephalus ganapatii have been investigated using manometric and electrophoretic techniques. Phenol oxidase was found to have maximum activity at pH 7·4, the Michaelis constant for dopamine was 189 μM and the enzyme was stable between 20 and 40°C. Potassium cyanide, sodium diethyldithiocarbamate and phenylthiourea strongly suppressed enzyme activity. The Ki values for potassium cyanide, diethyldithiocarbamate and phenylthiourea were 33μM, 700 μM and 938 μM respectively. The properties of soluble and insoluble enzymes to various phenolic substrates are discussed.

Groups of ten cattle were exposed to 0, 40 and 400 adult Rhipicephalus appendiculatus feeding once a week for 24 weeks. Although no differences in cumulative percentage weight gain were found at the end of the experiment, animals free of ticks performed better during the first 12 weeks. A marked recovery of the 400-tick group was recorded during weeks 13–24 and after ticks were removed. Haemoglobin and packed cell volume values were lowered in tick-infested animals but no clear trends were observed in red and white blood cells. No differences between the percentages of ticks feeding in the 2 tick-infested groups on day 2 were observed but higher numbers of females were feeding on the 40-tick group on day 5. More ticks were found on day 5 after tick application to the cattle during weeks 1–6 than in the rest of the experiment. Significant correlations were found between lymph node enlargement and ear damage when they were tested against tick load. R. appendiculatus nymphs feeding on the formerly tick-infested cattle were fewer, lighter and engorged in a shorter time than those on the control animals. The possible causes for the reduction in ticks feeding, the changes in cattle weights, blood composition and development of host resistance are discussed.

Twenty-three years ago, the first and only report of synergism between malarial and coccidial infections in chickens was published. In view of the potential commercial importance of this possible parasitic interaction in some parts of the world, and the lack of further supporting publications, this disease complex has now been reconsidered. An experiment on Plasmodium gallinaceum and Eimeria acervulina revealed no interaction of any kind between these species and a re-examination, with statistical analysis, of the raw data on which the original publication was based shows that no evidence of synergism between malarial and coccidial infections in chickens has so far been produced.

When I graduated as a Veterinary Surgeon some 36 years ago, the number of effective anti parasitic components available for clinical use were remarkably few. Many natural products were still in use (extract of male fern, arecoline, oil of chenopodium, kamala, nicotine, derris and the like) many difficult to formulate and to administer, some requiring overnight fasting before use and purgation after use. The compounds of remarkable promise at that time were phenothiazine for nematodes in farm animals, carbon tetrachloride for liver fluke in sheep and cattle, the sulpha durgs for coccidia and two wonder drugs for the arthropods, DDT and BHC.

The serum from rats infected intraperitoneally (i.p.) and subcutaneously (s.c.) with the tetrathyridia of Mesocestoides corti was analysed for α-amylase, alkaline phosphatase, γ-glutamyltransferase, glucose, corticosterone and total proteins. A histochemical analysis for hepatic alkaline phosphatase was also carried out. A significant decrease in activity of serum alkaline phosphatase was detected in both the i.p. and s.c. infections, whereas a large increase in hepatic alkaline phosphatase was observed in i.p. infections. A significant increase in serum cortiscosterone was found in both the i.p. and s.c. infections. No changes were detected in the other four components. The relevance of these findings is discussed with respect to the host–parasite relationship.

The major health problems of the world today relate to infections—viral, bacterial or parasitological. Malaria, schistosomiasis and filariasis are a risk to at least 600 million people and the problems of many of these infections are getting worse owing to ecological changes associated with industrial development and burgeoning populations which have increased out of proportion to increases in health resources.

Clones of single oocysts, single sporocysts, single sporozoites, single proliferative parasites, single cysts and single cystozoites of Isospora (Toxoplasma) gondii (KB-strain) were made under visual control using a de Fonbrune micromanipulator. Cloning was successful in 28, 32, 21, 8, 54 and 7% of the trials, respectively. All clones were used for monoclonal infection in non-immune conventionally reared (CV) or specified pathogen-free (SPF) cats. Pre-patent and patent periods, sporulation percentages of excreted oocysts, mouse infectivity of sporulated oocysts, antibody response and immunity to reinfection of CV cats were determined. For these parameters almost no differences were observed between monoclonal infections and infections described with the non-cloned KB-strain. In all cats autopsied during the patent period, 5–8 days post-infection, macrogametes, microgametes and oocysts were found. Since meiosis occurs during sporulation and since all free-living and intermediate host stages proved to be bisexual, it is concluded that sex differentiation in I. (T) gondii is not determined by segregation of sex chromosomes or sex genes but is caused by some final host factor(s) that induce(s) differential gene expression in genetically identical cells.

Swiss mice with chronic Trypanosoma brucei infections become refractory to subsequent infection with Babesia microti and B. rodhaini. Infection with B. microti 7 days after T. brucei resulted in an obvious inhibition of the babesia parasitaemias and this inhibition became more profound as the time interval between the infections increased, until at 17–20 days the parasitaemias were totally abolished. Even after intravenous injection of large numbers of parasites parasitaemias were inhibited. Similar inhibition was obtained in BALB/c mice but not in C57BL/6 mice. Mice with established T. brucei infections also showed reduced susceptibility to B. rodhaini. In mice similarly infected with T. brucei and the malaria parasites Plasmodium chabaudi chabaudi and P. c. adami the pre-patent periods were noticeably prolonged but the subsequent parasitaemias were unaffected. Infections with P. yoelii were unaffected. Trypanosoma brucei infections were not affected by the intracellular parasites. Among the mechanisms investigated to explain these findings were changes in red blood cell populations, cross-reacting antigens, the release of toxic factors and the generation of activated oxygen species. None of these could account for the inhibition observed.

General nutritional effects on female CFLP mice harbouring larval Taenia crassiceps were investigated using groups of mice fed ad libitum on purified diets containing 2%, 4%, 8% and 16% (w/w) protein respectively. When uninfected and infected mice were compared over an experimental period of 20 weeks, it was established that a significantly higher proportion of uninfected mice survived the course of the experiment than infected mice. There was no evidence of the presence of the parasites having any effect on the overall food intake of the mice. Infected mice, however, were found to be significantly heavier, on a fresh weight basis, than their uninfected partners, but the pattern was reversed when the dry weights of mouse carcasses were compared following the removal of parasites. In general, more parasite tissue was recovered from mice feeding on the higher protein diets (8% and 16%).

Relapse of infection after trypanocidal drug treatment of trypanosome infections is normally attributed to drug resistance on the part of the parasite, under-dosage of the drug, or reinfection of the host. We have demonstrated relapse infections in goats arising from none of these. Fourteen goats infected with Trypanosoma brucei suffered severe illness and 3 died within 45 days. Despite treatment with the trypanocidal drug Berenil, a 4th goat died 2 days later. Recovery of the remainder followed chemotherapy, and in 2 goats, necropsiecl 45 days after treatment, no trypanosomes or abnormalities were detected. However 2–3 months after Berenil chemotherapy, despite trypanosomes being undetectable in the blood during the intervening period, infections in 4 of the remaining 8 animals relapsed. At all stages of the primary and relapse infections, trypanosomes isolated from the blood of the goats were completely susceptible to Berenil when tested in mice, as were parasites isolated from cerebrospinal fluid and brain tissue at necropsy. At the time of treatment, only minimal cellular infiltration was found in the central nervous system (CNS), but death from the relapse infection was associated with a very severe meningoencephalitis. We conclude that the relapse infections were caused by the re-emergence of trypanosornes from the CNS, where sequestered parasites were inaccessible to the trypanocidal effects of the drug.

Just as human helminth infections are vitally influenced by the way in which people live, so the helminthiases of domestic animals depend on how these are managed.Veterinary helminthology is a branch of agriculture. The agricultural industry changes quickly, more quickly than the ideas of scientists. Ideas, in their turn change more rapidly than their practical implications are understood. A discussion of anthelmintic use must therefore be partly agricultural, partly historical.

Novel hydroxynaphthoquinones are reported with outstanding efficacy against Plasmodium, Eimeria and Theileria species. Biochemical evidence is presented for the selective toxicity of these compounds being due to inhibition of parasite respiratory systems.