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Biomedical subjects

I V Herbert

Publications and source records attributed to I V Herbert.

At least 19 recordsLinked to original sources
PubMed1991

Histochemical localisation of acid phosphatase and non-specific esterase in the midguts of two species of tick, Boophilus microplus and Rhipicephalus appendiculatus, as determined by light microscopy.

Serial sections of glycol methacrylate-embedded and frozen midguts of Boophilus microplus and Rhipicephalus appendiculatus were studied histochemically by light microscopy. The use of the naphthol AS-TR phosphate technique combined with glycol methacrylate embedding enabled the precise localisation of lysosomal enzyme activity, despite the ubiquity of haematin granules in tick midgut epithelia. The presence of acid phosphatase and non-specific esterase activity in the same cells was observed in all of the various developmental stages and feeding phases of the ticks. The pattern of appearance of these cells paralleled the reported level of protease activity in the midgut lumen. The cells were found to be solitary, particularly during the slow digestive phases, and appeared to move into the lumen, where they eventually disintegrated. The cells therefore appear to function as holocrine secretory cells. This is the first report indicating the presence of such secretory cells in the midgut of unfed ticks. The disintegration of these cells in the lumen suggests that lumenal digestion may be more important than hitherto realised.

Acid Phosphatase↗
PubMed1991

Acquired immunity to Toxocara canis infection in mice.

Acquired immunity develops against Toxocara canis infection in mice, and NIH mice are more immunoresponsive than CD1 mice. Twice infected NIH female mice showed 27% reduction in the total larval recoveries compared with non-sensitized controls. Twice-infected NIH male, and CD1 (both sexes) mice showed a negligible reduction in the total recoveries, though a significant (P less than 0.05) number of larvae were retained in the liver compared with the non-sensitized controls. All twice-infected mice showed a significant reduction in the number of larvae recovered from the brain compared with once-infected mice. Vaccination using ultraviolet irradiated embryonated eggs gave the best protection against reinfection. Excretory/secretory antigen afforded less protection, whilst whole adult worm vaccine and whole L2 culture vaccine gave no protection. Vaccinated mice had a higher 'free:penetrating ratio' of larvae in their intestine than similarly challenged but non-vaccinated mice. When the ileum was examined histologically 9 h post-infection, an inflammatory reaction was seen around the penetrating larvae in the sensitized and vaccinated mice but not in untreated controls, suggesting a role played by the intestine in the resistance against T. canis infection in mice.

Animals↗
PubMed1989

Resistance in cattle against Rhipicephalus appendiculatus with an assessment of cross-resistance to R. pulchellus (Acari: Ixodidae).

A comparison of the yield of engorged nymphs of Rhipicephalus appendiculatus and R. pulchellus was carried out between cattle highly resistant to R. appendiculatus but susceptible to R. pulchellus, and cattle and rabbits susceptible to both species. Resistant cattle yielded fewer and smaller R. appendiculatus nymphs than either susceptible cattle or rabbits. More nymphs of both tick species dropped from susceptible cattle but no differences were detected in the mean weight of engorged R. pulchellus nymphs fed on R. appendiculatus-resistant and susceptible cattle, although resistant animals yielded more nymphs of R. pulchellus than of R. appendiculatus. An acute inflammatory reaction, accompanied by intense pruritus and grooming, was observed in the ears of the resistant cattle infested with R. appendiculatus, but no reaction was detected in the opposite ears where R. pulchellus was feeding. The low cross-resistance between these two closely related tick species suggests that different antigens may be involved in the development of resistance in cattle to different tick species.

Animals↗
PubMed1989

Variations in innate resistance to experimental Toxocara canis infection in two strains of mice.

Strain-, sex- and age-based resistance of mice to Toxocara canis infection was demonstrated. Infection doses of similar numbers resulted in significantly (P less than 0.05) greater worm establishment in CD1 mice than in NIH mice, as well as a greater heterogeneity of responses between individuals. Male mice had significantly (P less than 0.05) fewer larvae in the brain and more larvae in the liver than female mice, when mice of greater than or equal to 3 months old were used. Appreciably more larvae were retained in the liver of male CD1 mice than in NIH mice. Orchidectomized mice had higher levels of brain infestation and a lower larval recovery from the liver compared with intact male mice. Infections in young mice of both strains showed more diversity in establishment and migration pattern between individuals than in older mice. Despite these differences in distribution of larvae and in the numbers recovered from experimental infections, the acute and chronic clinical signs observed in the two strains were very similar.

Age Factors↗
PubMed1988

The pathogenesis of Babesia motasi (Wales) infection in sheep.

Studies on the pathogenesis of Babesia motasi (Wales) infection following blood transfusion of infected blood to normal or splenectomised recipients showed that the intact animal is refractory to infection but that infection in splenectomised animals caused weight loss, fever, anorexia, lassitude and a macrocytic hypochromic anaemia which coincided with the peak of parasitaemia. There was an initial leucocytosis, largely due to a neutrophilia. The prepatent period following blood transfusion was 2-3 days. Unconjugated and conjugated (direct) bilirubin levels increased from pre-infection levels to peaks of 1.43 and 0.70 mg/100 ml of blood, respectively. Serum glutamic pyruvic acid transaminases (SGPT) increased slightly but serum glutamic-oxaloacetic acid transaminases (SGOT) and blood sugar (glucose) levels did not show significant changes after infection. Total serum protein levels increased temporarily and then returned to normal. Blood urea nitrogen levels increased, with biphasic peaks (76.32 and 86.29 mg/100 ml) on Days 2 and 8 post-patency. Clinical infections even in splenectomised sheep, were mild and of short duration, although recovered sheep remained carriers.

Alanine Transaminase↗
PubMed1988

Morphology and transmission of Theileria recondita (Theileriidae: Sporozoa) isolated from Haemaphysalis punctata from north Wales.

Adult Haemaphysalis punctata (Canestrini and Fanzago 1877) collected from an area of rough grazing at Mynydd Mawr, Aberdaron, North Wales, transmitted Theileria recondita (Wales); field-collected nymphs failed to transmit this parasite. Following adult tick infestation, piroplasms were first observed in the blood of splenectomised infested sheep 8 days after tick attachment; the parasitaemia lasted 9 days. The parasite can also be transferred by syringe passage of blood from splenectomised to normal sheep and vice versa. Parasitaemias were higher and of longer duration in splenectomised animals. A rise in parasitaemia was detected in a splenectomised ewe after parturition, 19 months following blood-transmitted infection from which it had recovered clinically. The morphometrics of the piroplasms of T. recondita (Wales) were investigated; the rod and the ring forms were the most common. The mean length of the rod form was 2.09 microns and the mean diameter of the ring form was 1.22 micron.

Animals↗
PubMed1988

Pathogenesis of infection with Theileria recondita (Wales) isolated from Haemaphysalis punctata from north Wales.

The pathogenicity of Theileria recondita infection in both splenectomised and non-splenectomised sheep was investigated. Following transmission of T. recondita to splenectomised animals both by adult ticks and blood transfusion a fever and severe macrocytic hypochromic anaemia developed which lasted the 9 days or more of patent infection. The prepatent period following tick attachment was about 8 days, but was variable following blood transfusion. Infection of normal animals caused a transient macrocytic hypochromic anaemia and slight fever which lasted throughout the period of low parasitaemia (7 days). The increase in mean cell volume was due to an increase in numbers of juvenile red cells in the peripheral blood. There was a transient neutrophilia and lymphocytopenia but no significant changes in thrombocyte or leucocyte numbers.

Animals↗
PubMed1988

The morphometrics of Babesia motasi (Wales) and its transmission by Haemaphysalis punctata (Canestrini and Fanzago 1877) to sheep.

Babesia motasi (Wales) was transmitted to sheep by larvae, nymphs and adult female Haemaphysalis punctata ticks which were either collected from rough grazing pasture, at Mynydd Mawr, Aberdaron, North Wales, or from laboratory cultures derived from ticks collected at the above site. Both transovarial and transstadial transmission of infection were demonstrated. Only larvae were shown to pick up infection. The parasite could not be demonstrated in intact sheep, either in blood films or following passage of whole blood from intact into splenectomised sheep. Organisms were detectable only in peripheral blood following blood transmission between splenectomised animals or in splenectomised sheep which were tick-infested. In such sheep a parasitaemia occurred 8-9 days after infected ticks started to feed and was accompanied by a mild fever. Splenectomised animals which recovered from acute infection remained as subclinical carriers but infection was eliminated with Ludobal, rendering animals resusceptible to infection. Morphological studies indicated that B. motasi (Wales) is similar to descriptions of isolates in Sweden, Holland and W. Germany but unlike an isolate from Turkey. The most common form is is a double pyriform with a mean length of 2.234 micron.

Animals↗
PubMed1987

Use of an oxfendazole pulse release bolus in calves exposed to natural subclinical infection with gastrointestinal nematodes.

During the first grazing season a group of calves treated with an oxfendazole pulse release bolus achieved a mean (+/- sem) weight gain of 140.7 (+/- 6.7) kg compared with 106.5 (+/- 5.7) kg by a group treated once with ivermectin mid-season, and 116.9 (+/- 6.9) kg by a group which received no treatment. This economic advantage was maintained during the period of winter housing. By the end of the second grazing season, during which the animals received no anthelmintic medication, they weighed on average 20 kg more than the wholly untreated group, a difference which was not statistically significant. No signs of clinical disease were observed in either the animals dosed with a pulse release bolus or the undosed control animals during the two year trial period. The treatment with the oxfendazole pulse release bolus greatly reduced the degree of pasture contamination in the first year but in the second year those animals that had been treated in the first year developed higher worm egg counts (P less than 0.001) and thus augmented the levels of pasture contamination compared with the untreated control animals. Nematodirus battus and N filicollis both produced low grade but fertile infestations in the calves.

Animals↗
PubMed1987

Sarcocystosis.

Sarcocystis infections of animals are commonplace and of worldwide distribution. Some species can be severely pathogenic to farm animals, causing anorexia, weight-loss, abortion and even death. But perhaps because sarcocysts are so common they have frequently been regarded as innocuous. Even in the USA and UK, many cases of abortion in farm animals go undiagnosed, and it is only now that sarcocystosis is being implicated as potentially of economic importance to the farm industry. In many cases however, the major effect is likely to be subclinical, seen in farm animals only as a reduction in liveweight gain. As this review shows, the history of research on Sarcocystis has been marked by confusion and neglect, although enormous progress has been made in the last decade. But until their economic importance is fully recognized, these widespread infections seem likely to continue unchallenged.

Journal Article↗
PubMed1987

Serodiagnosis of Babesia motasi (Wales), Theileria recondita (Wales) and Cytoecetes phagocytophila infection in sheep.

The indirect fluorescent antibody test (IFAT) was used to diagnose some tick-borne infections of sheep, Babesia motasi (Wales), Theileria recondita (Wales) and Cytoecetes phagocytophila. Antigen was prepared from blood derived from splenectomised sheep except for C phagocytophila which was derived from a normal animal. A field survey was made to assess the prevalence of B motasi and T recondita in North Wales and a comparison made between the titres using the B motasi (Wales) antigen with those previously reported. IFA titres reported in the homologous system were consistently lower than those described previously. The results of the field survey suggested that B motasi (Wales) infection is more widespread than was originally thought and more widespread than the known distribution of its vector Haemaphysalis punctata. No serological cross reactions occurred between B motasi (Wales), T recondita (Wales), C phagocytophila, B divergens, Sarcocystis ovicanis and Toxoplasma gondii.

Animals↗
PubMed1987

Effect of host resistance on the feeding and reproductive performance of Haemaphysalis punctata and Ixodes ricinus ticks.

A study was made to assess the influence of host response on Haemaphysalis punctata and Ixodes ricinus biology by comparing the effects of feeding ticks on previously uninfested hosts with those fed on previously sensitised hosts. Adult H punctata were fed on sheep; larvae and nymphs of H punctata and I ricinus were fed on rabbits. The engorgement weights of all instars studied that fed on sensitised hosts fell very gradually with successive infestations. These weight reductions were greater at high than at low levels of infestation. In previously sensitised hosts, the engorgement period of all instars was prolonged: the percentage of instars which completed engorgement and engorgement weights were reduced. The host's clinical and immune response markedly affected the fecundity of adult female ticks and the viability and hatchability of the laid eggs. Eighty per cent of female H punctata successfully laid eggs following the first infestation and the hatchability of eggs was 85 per cent. The numbers successfully laying eggs decreased to 60 per cent during the fifth and sixth infestations and was less than 20 per cent following the seventh infestation; the hatchability decreased similarly. There was no marked effect on the development of immature instars when fed on sensitised rabbits.

Animals↗
PubMed1987

Effect of Haemaphysalis punctata infestation on growing lambs and rabbits.

Lambs infected with adult Haemaphysalis punctata and rabbits infected with nymphs developed a macrocytic normochromic anaemia during seven and six successive infestations, respectively. The anaemia was directly proportional to the degree of infestation but disappeared several days after the termination of infestation. A leucocytosis, due to neutrophilia, was seen in both lambs and rabbits. Rabbits developed a thrombocytosis and reticulocytosis. Infested lambs grew less rapidly than uninfested animals. Signs of tick toxicosis and several other clinical manifestations appeared in both infested sheep and rabbits. Circulating antibodies against salivary antigen of adult H punctata were demonstrated in the sera of infested lambs by the micro-ELISA test. Titres were first detected on day 3 after infestation and increased gradually as infestation progressed. No precipitating antibodies in either infested sheep or rabbits were detected.

Anemia, Macrocytic↗
PubMed1986

Experimental microcyst sarcocystis infection in lambs: serology and immunohistochemistry.

Density gradient centrifugation using a performed self generated gradient of colloidal silica enabled the isolation of microscopic sheep sarcocystis cystozoites, free from heart muscle contamination. The efficiency of separation of cystozoites from residual heart muscle after digestion in pepsin and hydrochloric acid was 63 to 92 per cent. Antigens from cystozoites were used on enzyme-linked immunosorbent assays (ELISA) of plasma from six coccidia-free lambs infected once orally with 70,000 microcystic sheep sarcocystis sporocysts and for raising antisera in rabbits. Use of an anti-sheep IgM conjugate in the ELISA showed that anti-sarcocystis IgM production was transitory, appearing five to 10 days after infection, peaking in concentration at 42 days and following the peak of the acute phase of infection (32 and 33 days) in the lambs. In contrast, total anti-sarcocystis immunoglobulins, detected by ELISA, increased from five to 21 days after infection and continued to increase until the lambs were killed (the last at 81 days) and was more useful in diagnosing chronic infection. No cross reactions between microcystic sheep sarcocystis and Toxoplasma gondii or Eimeria species of sheep were observed. A peroxidase anti-peroxidase test, using rabbit anti-sarcocystis sera, detected second generation meronts and sarcocysts in fixed tissues from infected lambs making it useful for the diagnosis of acute or chronic disease post mortem.

Animals↗
PubMed1984

The migration of larval Toxocara canis in mice. I. Migration through the intestine in primary infections.

Toxocara canis second stage larvae (L2) hatched in the stomach of mice and within 2 h reached all parts of the small intestine, the posterior half being the preferred site for larval penetration. Following penetration at the base of crypts of leiberkuhn they followed tortuous routes in the lamina propria, and entered the tunica muscularis obliquely. Larvae only appeared to be arrested in their migration in the submucosa and lamina propria by an inflammatory reaction composed mainly of lymphocytes and eosinophils. Larvae were seen entering and within lymphatic vessels as well as the peritoneal cavity and invasion of the vascular system followed though actual penetration of intestinal blood vessels was not seen. Proteolytic enzyme activity was detected in culture media in which L2 larvae were maintained.

Animals↗
PubMed1984

The migration of larval Toxocara canis in mice. II. Post-intestinal migration in primary infections.

Following oral infection of NIH mice with Toxocara canis embryonated eggs the L2 pass the visceral phase of migration during te first week of infection. Larvae reach the liver and lungs and peak in number in these organs 2 and 3 days after infection, respectively. Larvae are then dispersed throughout the body and enter the myotropic--neurotropic phase by the 7th day of infection. Larvae injected directly into the brain are capable of migrating into the viscera and musculature. Considerable pathology occurs due to larval migrations, especially through the liver and lungs, and both acute and chronic disease are recorded. Studies of infections extending over a year show that the number of recoverable larvae declines gradually with periods of stable populations. On Days 3, 4 and 5 after infection, larvae were demonstrable in the faeces of infected mice. Prenatal infection was observed in a third of the offspring of mice infected the same day as conception.

Animals↗