Toxoplasma gondii is an obligate intracellular protozoan parasite. The objective of the present study was to examine the behaviour of Toxoplasma gondii RH Ankara strain tachyzoites in a cell culture environment. The study represents the first step in determining whether T. gondii RH Ankara strain tachyzoites, grown in cell culture, are of sufficient quality to allow cessation of in vivo tachyzoite production for diagnostic assays. In the present study, T. gondii RH Ankara strain tachyzoites were continuously produced in myeloma X63.Ag8.653, HeLa, Hep-2, and Vero cell cultures for 2 months. The average size of the tachyzoites was 3×5·7 μm prior to the first inoculation but after continuous production, a marked decrease was noted in average tachyzoite size. The smallest tachyzoite size, was 1×2·1 μm after 2 months, in myeloma cell cultures even though the yield of tachyzoites increased. With other cell cultures, tachyzoite yields were not as high as myeloma cell culture although decrease in size was less. The smallest decrease in tachyzoite size, averaging 2×3·8 μm after 2 months, was observed in tachyzoites produced in HeLa cell cultures. A virulence assay in small groups of BALB/c mice, using tachyzoites derived from cell cultures, was also conducted. The preliminary results of the virulence assay suggest that as the size of the tachyzoites decreased, the virulence in mice decreased. Future research will focus on the effect of the size of cell culture-derived T. gondii RH Ankara strain tachyzoites on the virulence, protein expression, and the reliability of diagnostic assays. Ultimately, the behaviour of tachyzoites from various T. gondii strains will be observed in cell culture to determine if size is altered.

Scattered records of parasitic species infecting commercially important marine fishes in sub-Saharan Africa are known from just a few countries where concerted efforts have been made by local parasitologists (e.g. Senegal, Nigeria, South Africa). Most of these consist of taxonomic records or general surveys of parasite faunas associated with marine hosts, which may or may not have been of commercial value. Little to no multi-disciplinary research is conducted in most parts of sub-Saharan Africa and hence parasitological data are not commonly used to advise fisheries management procedures. This review summarizes current knowledge on all parasitological research associated with commercially important marine fish species in sub-Saharan Africa.

Scabies is a parasitic disease caused by the ectoparasite Sarcoptes scabiei, affecting different mammalian species, including rabbits, worldwide. In the present study, we cloned and expressed a novel inorganic pyrophosphatase, Ssc-PYP-1, from S. scabiei var. cuniculi. Immunofluorescence staining showed that native Ssc-PYP-1 was localized in the tegument around the mouthparts and the entire legs, as well as in the cuticle of the mites. Interestingly, obvious staining was also observed on the fecal pellets of mites and in the integument of the mites. Based on its good immunoreactivity, an indirect enzyme-linked immunosorbent assay (ELISA) using recombinant Ssc-PYP-1 (rSsc-PYP-1) as the capture antigen was developed to diagnose sarcoptic mange in naturally infected rabbits; the assay had a sensitivity of 92·0% and specificity of 93·6%. Finally, using the rSsc-PYP-1-ELISA, the Ssc-PYP-1 antibody from 10 experimentally infected rabbits could be detected from 1 week post-infection. This is the first report of S. scabiei inorganic pyrophosphatase and the protein could serve as a potential serodiagnostic candidate for sarcoptic mange in rabbits.

In a paper published in April, 1910, I described and figured a new intracorpuscular parasite found in smears made from the spleen and liver of a jackal (Canis adustus), the animal having been shot by Mr W. F. Cooper in British East Africa. As I stated at the time, I hesitated about referring the parasite to the genus Piroplasma, and only did so provisionally because it offered a resemblance to two parasites found in the internal organs of one of my dogs which had “recovered” from P. canis infection. I, however, added: “Should future investigation prove that the parasite of the jackal differs from the types of P. canis encountered in ‘salted dogs’ I would propose to refer it to a new genus, Rossiella (Rossia being preoccupied) in view of its specific name.”

Experimentally we have demonstrated what Lee (1969, 1971 a, b) postulated on the basis of morphological considerations. The female heterakid is capable of transmitting H. meleagridis from the bird to the caecal worm egg without the intervention of the male except for fertilization. If the male is otherwise involved in the transmission of H. meleagridis, it seems unlikely that its role is of appreciable significance in the life-cycle of the histomonad as we know it now. However, if as believed by many, the histomonad was originally a parasite of a nematode that may not have been an obligatory parasite, the role of the male worm may have been considerably more important to the survival of the histomonad.

A previous study has shown that, under natural conditions, energy reserves of the desert toad, Scaphiopus couchii, are negatively related to the density of infection by Pseudodiplorchis americanus. However, this was based predominantly on collections of active animals from breeding congregations and inevitably selected toads which were in good condition. The parasite, a blood-feeding monogenean, occurs in burdens of up to 30 worms/host (mean intensity 6 worms/host) and represents a significant drain on reserves because the host does not feed during a 10-month hibernation. Field studies cannot resolve the possibility that larger worm densities are not observed in nature due to parasite-induced host mortality. The present study was conducted during investigations of P. americanus development and survival under controlled laboratory conditions, utilizing experimentally infected hosts which created worm densities larger than those observed in natural populations. At all temperature regimes, infected animals had smaller fat bodies than those uninfected but differences were generally not statistically significant due to large individual variations, presumably resulting from variations in past feeding efficiency. At cool temperatures (15–20 °C) there was no density-dependent effect on host fat body weight, and at a diurnal temperature cycle of 20–34 °C (simulating that experienced by host and parasite during the summer months), the effects of high temperatures were greater than the effects of infection, due to increased toad metabolic rates. The most significant effects of P. americanus were observed in hosts that began hibernation in relatively poor condition and experienced moderate temperatures (25 °C) during hibernation. The toads generally maintained packed blood cell levels (PCV) levels even when fat body weights were low, but infected animals had a lower PCV irrespective of fat body levels. In animals unfed after field collection, PCV was reduced in uninfected toads and was even lower in infected animals. Although very heavily infected toads (burdens of 35–95 worms/host) were generally in poorer condition than uninfected toads they still survived long-term hibernation under extreme nutritional stress. This study therefore confirmed observations made in field studies that there is a density-dependent relationship between the hosts' survival prospects and P. americanus infection. However, given the large variability in feeding efficiency and stored resources between individual toads, there is no evidence that the most heavily infected toads would have been unrepresented in field samples due to parasite-induced mortality.

1. The seasonal variations and regional distribution of the cattle lice have been studied by monthly examinations of cattle at the Cooper Field Research Station.

2. Additional evidence has been obtained by the distribution of a questionnaire to farmers, the general results of which are included in this paper.

3. The seasonal variations of the populations of the four species of cattle lice in Great Britain are similar. The maximum population density is reached in February and March. In April and May there is a rapid decline until the populations reach their lowest level in June, July and August. In September, the lice start increasing in numbers till they reach their maximum density in February and March.

4. The regional distribution of the population varies in accordance with the seasonal variations of the whole population.

5. The various climatic factors that may affect the lice populations are discussed. It is considered that the light intensity is a factor of major importance in this country.

6. The various factors inherent in the host animal are discussed, and it is suggested that the seasonal fluctuations of the density of the animal's coat are important.

7. The finding of a previous paper (Craufurd-Benson, 1941) that the microclimatic temperature is important as affecting the hatching of eggs is discussed in relation to the variations of lice populations as a whole.

The excreted/secreted proteinases of Haplometra cylindracea maintained in vitro, were found to hydrolyse the fluorogenic substrates, Z-ArgArg-NHMec and Z-PheArg-NHMec. This activity was shown to be typically that of cysteine proteinases, as turn-over of both substrates could be blocked by pre-incubation with peptidyl diazomethyl ketones. The biotinylated affinity reagent, biotin-Phe Ala-DMK, used in combination with Z-PheTyr(OBut)-DMK, was employed for the labelling and characterization of these cysteine proteinase activities. Three cathepsin B-like species were detected, with molecular weights of 48, 22–23 and 14 kDa, together with a cathepsin L-like enzyme, with a molecular weight of 55 kDa. The proteinases were also found to have hydrolytic activity towards the substrate, Z-GlyGlyArg-NHMec, which could be blocked by pre-incubation with either of the serine proteinase-selective reagents, Z-ArgP(OPh)2, or biotin-LysP(OPh)2, showing the activity to be trypsin-like. Using the biotinylated affinity label to characterize the trypsin-like enzymes revealed two molecular species with molecular weights of 20 and 24 kDa.

Four acidic glutathione (GSH) transferase forms were isolated from the cytosol of the adult cestode Hymenolepis diminuta by hydroxylapatite chromatography, glutathione-affinity chromatography and chromatofocusing, pH 7–5. The enzymes were dimers of subunit size approximately 24 kDa and accounted for at least 3% of the total soluble protein. The major GSH transferase had limited catalytic activity but may interact with a range of ligands and function as a binding/passive detoxification protein. An endogenous factor interfered with the binding of the crude cytosolic GSH transferase activity to glutathione-dependent affinity matrices but, following partial purification, the GSH transferase activity successfully interacted with the glutathione affinity matrix.

In the course of their investigations upon different species of Piroplasma numerous observers have kept infected blood in the ice-chest, or at room temperature, for various periods of time prior to the inoculation of animals. On the evidence afforded by microscopic examination alone some observers have concluded that the parasites are capable of considerable multiplication in defibrinated blood kept in vitro. Under these conditions many corpuscles undergo haemolysis and in consequence the parasites appear to be more numerous. We believe that this source of error explains the conclusions arrived at by Lignières and others with regard to the multiplication of P. bovis in extravascular blood (see p. 253).

Nosema algerae and N. eurytremae were successfully cultured in embryonic rat brain, Xenopus XTC-6 and Chang liver cells, and in embryonic rat brain and XTC-6 cells respectively. No parasites grew in cultures incubated at 38 °C but development took place in cells incubated at 34 °C and 27 °C. Increased levels of infections of the cultured cells were achieved by centrifugation of the spores on to the cells. The level of infection was also related to the type of medium used for hatching the spores, modifies NMRI giving better results than Leibowitz L15, and to the interval between adding the spores to the cell cultures and centrifugation.

An account is given of the occurrence of Parabothrium gadi-pollachii and Abothrium gadi in some members of the Gadidae caught in the north-eastern Atlantic.

The external features, musculature, excretory, nervous and genital systems of the two species are described in detail.

The adults of both species are characterized by the absence of a typical pseudophyllidean scolex and possess interesting modes of attachment to the intestine and caeca of the host. The variation found in individuals of A. gadi from the cod and haddock is discussed.

The new species of Trypanosoma described in this paper is parasitic in the blood of Ophicephalus ( = Ophiocephalus) striatus Bl., an air-breathing teleostean ‘Serpentfish’ found extensively in the fresh waters of India. This fish is one of the important food-fishes of India, especially in areas far away from the sea, which are mainly served by inland fisheries. It is equipped with an elaborate accessory air-breathing organ and therefore survives when taken out of water and kept in a moist condition. This hardiness of the fish has made it a popular item of diet since it is available in the hottest months of the summer in a fresh condition or even alive. With the expansion of the inland fisheries of India the importance of fishes of the genus Ophicephalus is also on the increase.

Lecithodendrium linstowi is one of the most prevalent and abundant trematodes of bats, but the larval stages and intermediate hosts have not been identified. We present the first molecular and morphological characterization of the cercariae of L. linstowi based on a phylogenetic analysis of partial fragments of LSU and ITS2 rDNA. The first intermediate host was incriminated as Radix balthica by DNA barcoding using cox1 and ITS2 sequences, although the snail morphologically resembled Radix peregra, emphasizing the requirement for molecular identification of lymnaeids as important intermediate hosts of medical and veterinary impact. The application of molecular data in this study has enabled linkage of life cycle stages and accurate incrimination of the first intermediate host.

Although Sarcocystis infections are very common in the muscle of mammals, and to a less extent of birds, in reptiles they have oniy rarely been seen. In a list given by Wenyon (1926) only two forms are recorded, namely from the muscles of Africaii geckoes and of the lizard Gongylus. The form here described was found in fairly large numbers in the striated muscle tissue of the Australian carpet snake Python spilotes. For the parasite the name Sarcocystis pythonis is suggested.

The bladder of the cysticerci, the larvae of cestodes, is a transitory embryonic organ; its morphology is related to its mode of development and the localization of the parasite in its intermediate host. The bladder makes possible the adaptation of the cysticercus to unusual conditions of its development. A certain degree of analogy between the trophoblast of the mammalian embryo and the bladder of the cysticerci adapted to the development in the tissues of mammals can be drawn.

In developing countries, estimates of the prevalence and diversity of Leptospira infections in livestock, an important but neglected zoonotic pathogen and cause of livestock productivity loss, are lacking. In Madagascar, abattoir sampling of cattle and pigs demonstrated a prevalence of infection of 20% in cattle and 5% in pigs by real-time PCR. In cattle, amplification and sequencing of the Leptospira-specific lfb1 gene revealed novel genotypes, mixed infections of two or more Leptospira species and evidence for potential transmission between small mammals and cattle. Sequencing of the secY gene demonstrated genetic similarities between Leptospira detected in Madagascar and, as yet, uncultured Leptospira strains identified in Tanzania, Reunion and Brazil. Detection of Leptospira DNA in the same animal was more likely in urine samples or pooled samples from four kidney lobes relative to samples collected from a single kidney lobe, suggesting an effect of sampling method on detection. In pigs, no molecular typing of positive samples was possible. Further research into the epidemiology of livestock leptospirosis in developing countries is needed to inform efforts to reduce human infections and to improve livestock productivity.

Pathological manifestations occasioned by mites of the genus Demodex are reported from Antechinus stuartii, a marsupial mouse. Derangements from single mite invasion of a hair follicle to massive nodule formation are detailed. In heavy infestations mites are found well distributed in the skin of the body with nodules limited, however, to the head, hind legs, around the base of the tail, the cloacal regions and, in females, just anterior to the pouch area.

Mites invade the hair follicle, where increase in their numbers leads to hypertrophy of the follicular epithelium which forms marked lobules surrounded by heavily vascularized connective tissue. It is thought that destruction of the lobule cells and penetration of the blood vessels due to increased mite numbers and activity leads to leucocytic infiltration with destruction of the mites and nodule deflation. In two instances of nodule deterioration a thickened skin plaque with markedly reduced mite populations remained in place of the nodule.

Gross symptoms of demodicidosis are occasionally marked in animals maintained in the laboratory but have not been found in specimens from the field. This suggests that environmental or dietary factors may be important in the onset of gross symptoms of demodicidosis.

This investigation was supported in part by a National Science Foundation (U.S.A.) grant (G-23321) and by a Commonwealth Scientific and an Industrial Research Organization (Australia) grant for marsupial research to the Zoology Department, A.N.U.

Dr Herman Beerman, Professor and Chairman, Department of Dermatology, Graduate School of Medicine, University of Pennsylvania, very kindly read and criticized our interpretation of the pathology. We are grateful for his help.

We would like to thank Margaret Dahlquist, Research Assistant, for her excellent technical assistance in the preparation of material for this report.