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PubMed1992

The efficacy of an albendazole intraruminal controlled-release device against gastrointestinal parasitism in lambs.

The effectiveness of albendazole in a controlled-release bolus in controlling gastrointestinal nematodes in lambs was assessed during the summer of 1986. Faecal egg counts were almost entirely negative throughout in the treated group and larval challenge remained low at below 2000 larvae kg-1. Untreated control lambs showed a characteristic pattern of auto-infection, culminating in a peak pasture larval count of over 70,000 larvae kg-1 and an outbreak of parasitic gastroenteritis in September associated with a serum pepsinogen concentration of 1.183 IU tyrosine and a mean worm burden of 91,165 nematodes at necropsy, including Ostertagia, Trichostrongylus and Nematodirus species. Subject to the restrictions imposed by the size of the bolus, this was considered to be a highly effective method of seasonal parasite control.

Abomasum↗
PubMed1975

The control of adult parasitic nematodes of cattle with morantel tartrate.

The anthelmintic efficacy of morantel tartrate at 5mg/kg bodymass was investigated in three separate controlled trials comprising 68 calves. High anthelmintic activity was established against adult Haemonchus placei, Ostertagia ostertagi, Cooperia spp. (C.pertinata and C. punctata), Bunostomum phlebotomum and Oesophagostomum radiatum.

Animals↗
PubMed1992

Overberg research projects. XII. The efficacy of an albendazole slow-release capsule in the control of nematode parasites of sheep.

Albendazole intra-ruminal slow-release capsules (SRC) administered to sheep grazing on irrigated pastures in the southern Cape Province, controlled Trichostrongylus for 91 d and Haemonchus and Teladorsagia for 61 d. Treating sheep with the SRC at 47 to 61 d intervals over a period of 10 months, significantly (P less than 0.05) reduced the infective potential of the pasture. Compared with sheep which received 2 disophenol and 3 broad spectrum anthelmintic treatments during the same period, the SRC reduced the infective potential of the pasture by 71.6%, while weekly drenching with albendazole over the same period, resulted in a significant (P less than 0.05) increase (73.4%) in the infective potential of the pasture.

Albendazole↗
PubMed1995

New geographical approaches to control of some parasitic zoonoses.

The advent of new technology for geographical representation and spatial analysis of databases from different sectors offers a new approach to planning and managing the control of tropical diseases. This article reviews the geographical and intersectoral aspects of the epidemiology and control of African trypanosomiasis, cutaneous and visceral leishmaniasis, Chagas disease, schistosomiasis, and foodborne trematode infections. The focal nature of their transmission, increasing recognition of the importance of animal reservoirs, and the need to understand environmental factors influencing their distribution are common to all these diseases. Geographical information systems (GIS) open a completely new perspective for intersectoral collaboration in adapting new technology to promote control of these diseases.

Chagas Disease↗
PubMedDate not supplied

The prospects for biological control of the free-living stages of nematode parasites of livestock.

Control of nematode parasites of livestock is focused almost entirely on the parasitic stages within the host. Current methods rely on anthelmintic drugs, but these are under increasing threat with the development of resistance covering the whole spectrum of anthelmintics amongst the important nematode species of a range of livestock. However, invariably the greatest proportion of the parasite biomass resides not within the animal hosts, but in the external environment-commonly on pasture. It is in this environment that the free-living stages are vulnerable to a range of abiotic factors (extremes in temperature and desiccation) and biotic factors (macro- and micro-organisms) that may decimate their numbers. Of the latter, there are organisms, which exert their effects either indirectly by rendering faecal deposits inimical for the development of nematode eggs through to infective larvae, or directly by acting as pathogens or by exploiting the free-living stages as a food source. Within this vast assemblage of organisms, which include microarthropods, protozoa, viruses, bacteria and fungi, could well emerge a variety of biological control agents of nematode parasites. At present, greatest interest lies with the nematode-destroying fungi. Work has progressed from Petri dishes, to plots, to paddocks with several species of the genus Arthrobotrys and Duddingtonia flagrans. These studies indicate that the voracious nematophagous capabilities of these fungi, clearly demonstrated in vitro, translate to reductions in the number of infective larvae on pasture and indicate that levels of control, comparable to conventional schemes using anthelmintics, can be achieved. The challenge now lies in developing methods of administration of fungi to animals which can be applied under practical farm conditions. However, the pursuit of candidates for biological control of nematode parasites of livestock should not involve just a few species of nematophagous fungi. More than 100 species of fungi have been identified as possessing nematode destroying capabilities. These need to be more specifically investigated for their effects on free-living stages of nematode parasites of livestock, together with other classes of organisms, particularly bacteria, which have proved successful as biological control agents of arthropods.

Animals↗
PubMed2006

Biological control of sheep parasites using Duddingtonia flagrans: trials on commercial farms in Sweden.

Trials were conducted on 3 commercial sheep farms in Sweden to assess the effect of administering spores of the nematode trapping fungus, Duddingtonia flagrans, together with supplementary feed to lactating ewes for the first 6 weeks from turn-out on pastures in spring. Also control groups of ewes, receiving only feed supplement, were established on all 3 farms. Groups were monitored by intensive parasitological investigation. The ewes and their lambs were moved in late June to saved pastures for summer grazing, the lambs receiving an anthelmintic treatment at this time. After approximately 6 weeks on summer pasture the lambs were weaned, treated a second time with anthelmintic, and returned to their original lambing pastures for finishing. Decisions as to when lambs were to be marketed were entirely at the discretion of the farmer co-operators. No difference in lamb performance was found between the two treatments on all three farms. This was attributed to the high levels of nutrition initially of the ewes limiting their post-partum rise in nematode faecal egg counts in spring, which in turn resulted in low levels of nematode infection on pastures throughout the autumn period. Additionally, pastures were of good quality for the lambs during the finishing period, so they grew at optimal rates as far as the farmers were concerned.

Animal Husbandry↗
PubMed2002

Molecular biological applications in the diagnosis and control of leishmaniasis and parasite identification.

Molecular biology is increasingly relevant to the diagnosis and control of infectious diseases. Information on DNA sequences has been extensively exploited for the development of polymerase chain reaction-based assays for the diagnosis of leishmaniasis and the identification of parasite species. It has also led to the use of cloned antigen for serodiagnosis. It is expected that the sequencing of the Leishmania major genome and the genomes of other Leishmania species will enable important progress in further improving diagnosis and control. The ability to use genome data to clone and sequence genes, which, when expressed, provide antigens for vaccine development, will increase the possibilities for rational vaccine development. Moreover, DNA on its own will provide the basis for the development of DNA vaccines that may overcome some of the problems encountered with protein-based vaccines. One of the greatest threats to parasite control is the development of drug resistance in parasites. Knowing the molecular basis of drug resistance and the ability to monitor its development with sensitive and specific DNA-based assays for 'resistance alleles' may aid maintaining the effectiveness of available anti-Leishmania drugs. Finally, techniques such as microarrays and nucleic acid sequence-based amplification will eventually allow rapid screening for specific parasite genotypes and assist in diagnostic and epidemiological studies.

Animals↗
PubMed1990

The chemical control of livestock parasites: problems and alternatives.

Over 200 classes of chemical compounds are currently in use for the treatment of livestock parasites. Here Les Strong and Richard Wall review some of the problems arising from the total reliance on chemical control and consider some of the alternative methods that might be given more thought and application.

Journal Article↗
PubMed2000

WAAVP/Pfizer award for excellence in veterinary parasitology research. My involvement in, and some thoughts for livestock parasitological research in Australia.

Being presented with the WAAVP Pfizer award for excellence in parasitological research is the pinnacle of my career. In accepting I acknowledge the support that I have received from workmates, colleagues, friends and family over the years that I have been involved in this field of endeavour. Parasitic disease is the most significant threat to the Australian sheep industry. A lack of understanding of drug action, the absence of epidemiologically-based treatment programs and incorrect or excessive chemical use has resulted in the development of worm, lice and blowfly parasites which are resistant to most existing chemotherapeutic compounds. During the past decade, difficulties in sustainable control of parasitic disease, the decline in demand for wool products and competition from less expensive synthetic fibre has halved the sheep population and profitability of the industry. Notwithstanding this, a 'right-sized', sustainable industry is emerging which will require effective chemotherapy to be the cornerstone of parasite control. Chemical intervention in parasitic disease is therefore here to stay but the paucity of new antiparasitic products in the short term dictates that present therapeutics are all that producers will have for the foreseeable future. This situation will necessitate innovative practices and formulations to provide more cost effective, efficient drug performance and to extend parasiticide life. However, the development of multiple drug resistance and reduction in funds for parasitological research seriously compromises our ability to confront these demands. With the patent life of all but the most recent macrocyclic lactone (ML) compounds lapsing, low cost development of bioequivalent generic formulations and options for innovative strategies to increase performance and market share are eagerly sought. The key to efficient drug use lies in a detailed understanding of the pharmacokinetic principles of drug action and the host animal's physiological responses to identify procedures which maximise drug availability--in essence giving the drug the best chance to work. It is therefore evident that the how, where and why of drug exchange between the bloodstream and the gastrointestinal tract are of such interest. Of particular importance is identification of the kinetic and dynamic behaviour of drug in the gastrointestinal tract (GIT) and the role of biliary secretion and metabolic fate of biliary (and non-biliary) compounds. The extent to which biliary secreted parent drug and/or metabolites are presented to the gut lumen, reabsorbed as free compound or after deconjugation by large bowel bacteria, and participate in the enterohepatic cycle is a major contributor to parasite exposure. Integrating parasiticide disposition with host physiology, particularly relating to such aspects as gastrointestinal function, feed intake and body condition has demonstrated the value of 'whole body' pharmacokinetic studies to identify processes to increase drug efficacy. Novel formulation modifications to provide 'targeted' drug delivery including carrier technology, sustained release devices and site-directed formulations can manipulate pharmacokinetic disposition to direct or extend drug availability to the parasite infection. These research directions should be undertaken as collaborative projects between research organisations and the veterinary pharmaceutical industry. With the identification of methods to improve drug action, emphasis must then be directed towards effective communication for their implementation. It will be vital that parasitologists move out of the laboratory to actively disseminate knowledge to the producer. We are ambassadors for our profession and if we fail to communicate well the perception, and indeed the value, of our work can be at risk.

Animals↗
PubMed1999

Can vector control play a useful supplementary role against bancroftian filariasis?

A single campaign of mass treatment for bancroftian filariasis with diethylcarbamazine (DEC) in Makunduchi, a town in Zanzibar, United Republic of Tanzania, combined with elimination of mosquito breeding in pit latrines with polystyrene beads was followed by a progressive decline over a 5-year period in the microfilarial rate from 49% to 3%. Evidence that vector control had contributed to this long-term decline was obtained by comparison with another town, Moga, where a DEC campaign was used without vector control and where resurgence of microfilariae could be observed 3-6 years after the campaign. In Zanzibar town, treatment of 3844 wet pit latrines and cesspits with polystyrene beads reduced the adult mosquito population in houses by about 65%. Supplementary treatment of open drains and marshes with Bacillus sphaericus produced little or no additional reduction compared to a sector of the town where only pit treatment with polystyrene was carried out. The cost and effort of achieving the 65% reduction in mosquito population could hardly be justified for its impact on filariasis alone, but its noticeable impact on biting nuisance might help to gain community support for an integrated programme.

Animals↗
PubMed1998

Resurgence of vivax malaria in Henan Province, China.

Henan Province (population, 90 million) in China has nonstable endemic malaria. After 1970 when 10.2 million cases of malaria were reported in the province, a huge control programme was undertaken, and in the mid-1980s indoor spraying and bednet impregnation with pyrethroids began. By 1992 only 318 cases were reported. In 1992 Henan declared "basic elimination of malaria" and in consequence spraying and bednet impregnation ceased after 1994. Subsequently, malaria broke out again in southern Henan. In 1995 we conducted a household survey for malaria transmission in southern Henan. Blood smears and serum samples for immunofluorescent antibody (IFA) testing were collected from 2329 people and 3.1% (73/2329) were positive for infection with Plasmodium vivax and 13% (301/2329) positive for malaria (titre > or = 1:20). All age groups were affected. Exophilic Anopheles sinensis occurs throughout the province; endo-anthropophilic A. anthropophagus, whose vectorial capacity is 20 times greater than that of A. sinensis, occurs mainly in southern Henan (S of latitude 33 degrees N) and was greatly reduced in numbers during 1985-92. Comparison of 1995 entomological data with historical data showed that A. anthropophagus increased in proportion to other anophelines after spraying activities and impregnation of bednets ceased. Over 10% of 9377 residents reported having malaria. The true number affected among the at-risk population of 700,000 must be larger. We conclude that impregnated bednets and malaria surveillance should continue even after an area is declared to have "basically eliminated" malaria.

Adolescent↗
PubMed2004

Destiny and intracellular survival of Leishmania amazonensis in control and dexamethasone-treated glial cultures: protozoa-specific glycoconjugate tagging and TUNEL staining.

Leishmania amazonensis, an obligatory intracellular parasite, survives internalization by macrophages, but no information is available on the involvement of microglia. We have investigated microglia-protozoa interactions in mixed glial cultures infected with promastigote forms of L. amazonensis after lipopolysaccharide (LPS) or dexamethasone (DM) treatment. After 2 hr of exposure to parasites in control cultures, there was a small number of infected microglia (1%). Preincubation with LPS or DM led to 14% or 60% of microglial cells with attached parasites, respectively. DM treatment resulted in 39% of microglial cells with internalized parasites (controls or LPS-treated cells had < or =1%). Scanning electron micrographs showed numerous filopodia in DM-treated cells, whereas these projections were rarely observed in LPS-treated or control cells. DM treatment also affected the intramicroglial survival of Leishmania. In control cultures, internalized parasites, tagged with an anti-lipophosphoglycan (anti-LPG) antibody, showed fragmented DNA [terminal deoxyribonucleotide transferase-mediated dUTP-X nick end labeling (TUNEL+)] after 4 hr of interaction, but changes seemed slightly delayed in DM-treated cultures. After 12 hr, there were no LPG+/TUNEL+ profiles in controls, whereas rare LPG+ profiles still persisted in DM-treated cells. Our results suggest that microglia are highly effective in the elimination of Leishmania and that the process can be effectively studied by LPG/TUNEL double labeling.

Adjuvants, Immunologic↗
PubMed1987

Control of gastrointestinal parasitism in calves in Sweden over six years using the morantel sustained release bolus.

During the 6 years 1979-1984, the use of the morantel sustained release bolus (MSRB) was monitored in first year grazing calves. Twenty-four to 30 calves each year were allotted to two groups (controls and MSRB-treated) and turned out at the end of May on the same pasture divided into two equal areas. After housing in October, each group was kept in boxes and fed concentrates, whey and hay. The calves were weighed at monthly intervals until the first animals were sent to slaughter. No cases of clinical ostertagiasis Type I were observed in the control calves during the grazing seasons, but in one year (1983) clinical signs occurred 2 weeks after housing. The number of overwintering larvae was influenced by pasture contamination the previous season and climatic conditions during winter and spring. The fecal egg output of the control animals during the grazing season did not reflect the level of pasture contamination at turnout. The build-up of pasture larval contamination during the later part of the grazing season was influenced by the climatic conditions. The fecal egg output of the treated calves was low during the entire grazing season resulting in a significantly reduced pasture contamination. A significantly reduced live-weight gain in the control calves was demonstrated at housing in five of the six years. When heavily infected at housing, the performance of the control calves was still influenced negatively during the fattening period indoors.

Animals↗
PubMed1999

A study of the cost effectiveness of selective health interventions for the control of intestinal parasites in rural Bangladesh.

The study examined the cost effectiveness of 4 different regimens in reducing the prevalence and intensity of infection of Ascaris lumbricoides, Trichuris trichiura, and hookworm over an 18-mo period in randomized community samples of children aged 2-8 yr living in rural Bangladesh. The household was the unit of randomization in each community. The 4 regimens were (1) only chemotherapy to all household members at the commencement of the study (i.e., at an interval of 18 mo), (2) same as group (1) and regular health education throughout the study period, (3) chemotherapy to all household members at the commencement of the study and subsequent chemotherapy to all children at intervals of 6 mo, and (4) same as group 3 with the addition of regular health education throughout the study period. Health education (through home and school visits and focus group discussions) was aimed at increasing awareness of worm transmission and the disabilities caused by intestinal helminths. Simple ways of improving personal hygiene and sanitation through hand washing, nail trimming, wearing of shoes, and use of a latrine and clean water supplies were encouraged. Because albendazole is a broad spectrum anthelmintic, the cost effectiveness of the 4 interventions were compared by the weighted percentage reduction in prevalence and the weighted percentage reduction in intensities of infection as measured by geometric mean egg loads of all 3 worms combined. The most cost-effective strategy was the single albendazole mass chemotherapy at an interval of 18 mo. The 2 regimens involving health education were the least cost effective.

Albendazole↗
PubMed1987

Efficacy of a morantel sustained-release bolus for control of gastrointestinal parasites in winter-grazed steers in Mississippi.

From Nov 22, 1983 through May 15, 1984, 36 crossbred steers were allotted into 3 treatment groups (12/group) and were grazed on separate 3.4-hectare pastures. On Nov 22, 1983, the steers were administered a single morantel sustained-release bolus (MSRB), orally (group 1), or a single dose of thiabendazole (TBZ; 66 mg/kg of body weight, orally; group 2), or were left untreated (group 3; controls). Animal weights, nematode egg counts in fecal specimens, and plasma pepsinogen concentrations were monitored monthly. At the termination of the study, 4 steers from each treatment group were slaughtered and necropsied and worm counts were determined. A set of parasite-free tracer calves (3/treatment group) were grazed with each treatment group for 1 month, beginning on Nov 22, 1983; a second set of tracer calves (3/group) were grazed with each treatment group for 1 month, beginning Apr 3, 1984. At the end of their respective grazing periods, tracer calves were held for 3 weeks and then were slaughtered and necropsied and their worm counts were determined. Mean nematode egg counts in fecal specimens of group 1 (MSRB treated) were significantly lower (P less than 0.05) than that of the TBZ-treated or nontreated steers. Differences in worm counts were not found between treatment groups. Differences in worm counts of tracer calves were not found among the 3 groups for November 1983 nor for April 1984. Steers treated with the MSRB had a higher mean weight gain (P less than 0.06) than did the control or TBZ-treated steers.

Animals↗