Ultrastructural effects of albendazole on the body wall of Gnathostoma spinigerum third stage larvae

This study investigated the effects of albendazole (ABZ) on the ultrastructure of Gnathostoma spinigerum advanced third-stage larvae. Two groups of experimentally infected mice received 60 or 90 mg/kg ABZ orally once a day for 21 consecutive days. Both groups had damage to the body walls of the worms, especially to the non-contractile part of the muscular layer. The severity of the damage was dose related, the higher the dose, the greater the damage. The body wall of the ABZ treated larvae demonstrated a decrease in the number of mitochondria in the non-contractile muscular part, especially in the internal surface of the sarcolemma. Some mitochondria developed large vacuoles, and became distorted and degenerated. The nuclei degenerated and had irregular shapes and the number of glycogen granules decreased. The present study demonstrates the structural damage induced by the toxic effects of ABZ and increases our knowledge of the mechanism of action of ABZ against G. spinigerum.

Effects of a combinations of emodepside and praziquantel on parasites of reptiles and rodents

A new combination of two anthelmintic compounds containing emodepside and praziquantel (Profender, Bayer AG, Levekusen, Germany) was tested in pet rodents and reptiles. Topical application of the two compounds led to the quick disappearance of nematodes and cestodes from a broad spectrum of hosts including mice, jirds, snakes, anole lizards, turtles, monitor lizards, etc. In reptiles the dosage had to be increased, since the thick outer layer of the epidermis hinders the penetration of the compounds. In animals with an extremely thick epidermis (e.g. monitor lizards, leguans) the new product was applied under the armpits.

Efficacy of a combination of imidacloprid and moxidectin against parasites of reptiles and rodents: case reports

A new compound containing imidacloprid 10% (w/v) and moxidectin 2.5% (w/v) (Advantage multi, Advocate) was applied as a spot-on treatment to mice experimentally infected with Trichuris muris. Case reports of reptiles found positive for nematode and mite infections following parasitological examination and treated with this compound are also discussed. The results demonstrated that the registered, recommended 2.5% moxidectin concentration for use in dogs was sufficient to eliminate nematodes and mites in reptiles. Infections with nematodes were successfully treated with a single application. Mite infestations in reptiles were eliminated using a treatment repeated on 3 consecutive days.

Mechanisms of action of emodepside

The research of the class of cyclic octadepsipeptides started at the beginning of the 1990s. PF1022A, the starting material of emodepside, is a natural secondary metabolite of the fungus Mycelia sterilia, which belongs to the microflora of the leaves of Camellia japonica. PF1022A consists of four N-methyl-L-leucins, two D-Iactic acids and two D-phenyllactic acids, which build up a cyclic octadepsipeptide with an alternating L-D-L-configuration. Emodepside is a semisynthetic derivative of PF1022A, which contains a morpholine attached in para position at each of both D-phenyllactic acids. Emodepside is efficacious against a variety of gastrointestinal nematodes. Emodepside binds to a presynaptic latrophilin receptor in nematodes. The following presynaptic signal transduction occurs via activation of Gqalpha protein and phospholipase-Cbeta, which leads to mobilization of diacylglycerol (DAG). DAG then activates UNC-13 and synaptobrevin, two proteins which play an important role in presynaptic vesicle-functioning. This finally leads to the release of a currently unidentified transmitter. The transmitter (or modulator) exerts its effects at the postsynaptic membrane and induces a flaccid paralysis of the pharynx and the somatic musculature in nematodes.

Early exposure of infants to GI nematodes induces Th2 dominant immune responses which are unaffected by periodic anthelminthic treatment

We have previously shown a reduction in anaemia and wasting malnutrition in infants <3 years old in Pemba Island, Zanzibar, following repeated anthelminthic treatment for the endemic gastrointestinal (GI) nematodes Ascaris lumbricoides, hookworm and Trichuris trichiura. In view of the low intensity of worm infections in this age group, this was unexpected, and it was proposed that immune responses to the worms rather than their direct effects may play a significant role in morbidity in infants and that anthelminthic treatment may alleviate such effects. Therefore, the primary aims of this study were to characterise the immune response to initial/early GI nematode infections in infants and the effects of anthelminthic treatment on such immune responses. The frequency and levels of Th1/Th2 cytokines (IL-5, IL-13, IFN-γ and IL-10) induced by the worms were evaluated in 666 infants aged 6–24 months using the Whole Blood Assay. Ascaris and hookworm antigens induced predominantly Th2 cytokine responses, and levels of IL-5 and IL-13 were significantly correlated. The frequencies and levels of responses were higher for both Ascaris positive and hookworm positive infants compared with worm negative individuals, but very few infants made Trichuris-specific cytokine responses. Infants treated every 3 months with mebendazole showed a significantly lower prevalence of infection compared with placebo-treated controls at one year following baseline. At follow-up, cytokine responses to Ascaris and hookworm antigens, which remained Th2 biased, were increased compared with baseline but were not significantly affected by treatment. However, blood eosinophil levels, which were elevated in worm-infected children, were significantly lower in treated children. Thus the effect of deworming in this age group on anaemia and wasting malnutrition, which were replicated in this study, could not be explained by modification of cytokine responses but may be related to eosinophil function.

Infants and very young children commonly become infected with intestinal nematode infections. However, the worm burdens are generally very light, so a beneficial effect of deworming on wasting malnutrition and anaemia in this age group which we have demonstrated was unexpected and the mechanism unclear. To investigate this, we have, for the first time, determined whether such worm infections in infants induce significant immune reactions which might be detrimental to nutrition and growth e.g. by inducing inflammation in the gut or by cytokine effects on erythropoiesis. We also determined if such responses are modulated by regular deworming over a 9 month period. Peripheral blood cells from infants infected with Ascaris and hookworms in particular responded to stimulation with worm antigens, producing predominantly Th2 cytokines. Although the Th2 cytokine responses in the periphery were not significantly altered by deworming, the levels of eosinophils, which are regulated by the Th2 cytokine, IL-5, were lower after treatment. It is possible that eosinophils play a role in gut pathology leading to wasting malnutrition and anaemia in the very young and that this effect is reduced by deworming.

The costs and cost-effectiveness of mass treatment for intestinal nematode worm infections using different treatment thresholds

Background

It is estimated that almost a half of all of people living in developing countries today are infected with roundworms, hookworms, or whipworms or combinations of these types of intestinal nematode worms. They can all be treated using safe, effective, and inexpensive single-dose generic drugs costing as little as USD 0.03 per person treated when bought in bulk. The disease caused by intestinal nematodes is strongly related to the number of worms in the gut, and it is typical to find that worms tend to be aggregated or clumped in their distribution so that <20% of people may harbour >80% of all worms. This clumping of worms is greatest when the prevalence is low. When the prevalence rises above 50%, the mean worm burden increases exponentially, worms are less clumped, and more people are likely to have moderate to heavy infections and may be diseased. Children are most at risk. For these reasons, the World Health Organization (WHO) currently recommends mass treatment of children ≥1 year old without prior diagnosis when the prevalence is ≥20% and treatment twice a year when the prevalence is ≥50%.

Methods and Findings

The risk of moderate to heavy infections with intestinal nematodes was estimated by applying the negative binomial probability distribution, then the drug cost of treating diseased individuals was calculated based on different threshold numbers of worms. Based on this cost analysis, a new three-tier treatment regime is proposed: if the combined prevalence is >40%, treat all children once a year; >60% treat twice a year; and >80% treat three times a year. Using average data on drug and delivery costs of USD 0.15 to treat a school-age child and USD 0.25 to treat a pre-school child (with provisos) the cost of treating children aged 2–14 years was calculated for 105 low- and low-middle-income countries and for constituent regions of India and China based on estimates of the combined prevalence of intestinal nematode worms therein. The annual cost of the three-tier threshold was estimated to be USD 224 million compared with USD 276 million when the current WHO recommendations for mass treatment were applied.

Conclusion

The three-tier treatment thresholds were less expensive and more effective as they allocated a greater proportion of expenditures to treating infected individuals when compared with the WHO thresholds (73% compared with 61%) and treated a larger proportion of individuals with moderate to heavy worm burdens, arbitrarily defined as more than 10 worms per person (31% compared with 21%).

Almost one in every two people in the developing world is infected with one or more types of intestinal nematode worms. When fewer than 50% of people are infected, most carry only a few worms; but when more than 50% are infected, the number carrying moderate to heavy numbers increases markedly, as does the risk of disease. The WHO recommends annual mass deworming of children when 20% or more are infected and twice a year if 50% or more are infected. We estimated the cost of this to treat children with 10+ worms, an arbitrary moderate to heavy infection. We concluded that it is not cost-effective to mass treat children when fewer than 40% are infected because the majority are uninfected and few are likely be diseased. We propose annual treatment when 40% or more children are infected, twice a year at 60%, and three times a year at 80% or more. This would cost USD 224 million annually to treat all children aged 2–14 years in 107 developing countries compared with USD 276 million using current WHO guidelines. The new three-tier guidelines also treat a larger proportion of infected children and treat children with moderate to heavy worm burdens more often.

Pyrantel in small animal medicine: 30 years on

Pyrantel, a tetrahydropyrimidine nicotinic agonist anthelmintic, has been used in companion animal medicine since the 1970s to control two important nematode groups, the hookworms and the roundworms. Given the zoonotic potential of these parasites, pyrantel has served a dual role in helping to protect the health of both companion animals and the public for more than 30 years. This review describes the history and mechanism of action of this drug, and collates evidence that resistance to pyrantel has developed in at least one canine nematode, the hookworm Ancylostoma caninum. The role of in vitro diagnosis tests in managing anthelmintic resistance in companion animal parasites is discussed, as are management practices that may reduce the rate at which resistance develops.

[Tribendimidine enteric coated tablet in treatment of 1,292 cases with intestinal nematode infection--a phase IV clinical trial]

OBJECTIVE

To further evaluate the efficacy and safety of tribendimidine in treatment of adult patients with intestinal nematode infections.

METHODS

An open and multi-center clinical trial was conducted in the provinces of Hainan, Sichuan and Guizhou. A total of 1,292 infected cases aged 15-70 years were enrolled in the study. Modified Kato-Katz method was used to diagnose the cases with intestinal nematode infections and assess the efficacy 3-4 weeks post treatment. Patients with Ascaris lumbricoides infection were treated orally with tribendimidine enteric coated tablets at a single dose of 300 mg, while in the patients with Ancylostoma duodenale, mixed A. duodenale and A. lumbricoides, or with other helminth infections, a single dose of 400 mg was administered.

RESULTS

The cure rate and effective rate of the patients with Ancylostoma infection were 88.4% (1,009/1,141) and 99.1% (1,131/1,141), respectively, while in patients with A. lumbricoides infection, they were 95.0% (419/441) and 99.8% (440/441), respectively. The cure rate of tribendimidine enteric coated tablet given to patients with Trichuris trichiura infection at a single dose of 400 mg was 76.8% (109/142). The adverse effect induced by tribendimidine was light and transient with a rate of 3.3% (42/1,292). No apparent impact was seen on blood and urine routine examinations, hepatic and renal functions as well as ECG examination.

CONCLUSION

It is further confirmed that under the used dosage for expanding treatment in larger sample of patients with various ages and infected with Ancylostoma duodenale, A. lumbricoides and other helminths, tribendimidine enteric coated tablet is safe with satisfactory efficacy.

[The investigation of short term efficiency of oxfendazole + oxyclozanide paste and tablet formulations against gastrointestinal nematodes in sheep]

The aim of this study was to investigate the effectiveness of tablet and paste formulations of Oxfendazole and Oxyclozanide combinations against subclinical gastrointestinal nematode infections and to compare the advantages and/or disadvantages of their use. Seventy-five infected sheep were selected from an enterprise located in Kayseri in 2006. The sheep were divided into 3 equal groups as paste, tablet and control groups. Fecal samples were collected from each group before drug administration. While the paste and tablet groups were administered drugs orally, no drugs were given to the controls. Fecal samples were collected on the 7th, 14th, 21st, and 28th days after drug application and the EPG values were determined. The parasitological examination revealed that the most prevalent species was Ostertagia spp., followed by Nematodirus spp. and Trichostrongylus spp. While the mean EPG value of the control group increased up to a ratio of 7.8% at day 28, the mean EPG values of drug groups decreased to 0%. Although the unit dose of paste formulation is more expensive, it was found that it could be an alternative to tablet formulation and has some advantages such as being easier to give, effective utilizing, shorter application period, fewer complications and death risk, no application failure and requires fewer personnel.

Some aspects of nematode infection in pigs from small herds

Two traditionally maintained, small herds from southern Poland, with 8 and 12 sows, respectively, were surveyed coprologically during 2006-2007. In one of the herds, while deworming a group of sows with levamisole, faecal samples were collected on Day -7, Day 0 (the day of treatment) and Day 10, in order to assess the therapeutic effect of the drug. Coprological investigation was performed also in 26 fatteners originating from other small farms and slaughtered in a local abattoir, with their intestines washed through for the presence of roundworms. In both herds examined, Ascaris suum and Oesophagostomum spp. were prevalent, whilst Trichuris suis appeared only very rarely. Mainly fatteners, replacement gilts and young sows were highly infected with A. suum. The roundworm occurrence in 2- 3-week-old piglets, with the intensity of 300 eggs per gram of faeces (EPG), indicated the possibility of parasite transmission to offspring very early in age. The highest level of Oesophagostomum spp. infection was observed in sows, but weaners were also much affected. For the group of dewormed sows, the mean faecal egg count reduction (FECR) was estimated to be 77.1- 80.4%, suggesting the presence of resistant nodular worms. A very high false-positive A. suum egg counts found in slaughtered animals (240 to 320 EPG) testified to a high contamination level of the environment of small piggeries, as well. Since the reciprocal transmission of parasites between pigs and poultry might occur, it implies that the flocks should be raised separately.

Use of topical selamectin for the treatment of Syphacia muris infection in laboratory rats

Efficacy of selamectin was studied in naturally acquired S. muris infections in rats. Fourty-eight S. muris-positive rats were divided into six treated and two control groups. Selamectin (6 mg/kg) was applied topically to the skin in a single spot at the base of the neck in the treatment group. The rats of treated and control groups were necropsied on the 24th day after the treatment. Topical selamectin was found to be 40.7-63.3% effective (based on egg per gram method) in eliminating S. muris infection in rats. The efficacy of the treatment against S. muris (based on adult worm counts) in male and female rats was 35.14-58.88%, respectively (mean 48.39%).

Anthelmintic resistance in cattle nematodes in northwestern São Paulo State, Brazil

The present study was carried out in the northwestern region of São Paulo State, Brazil, to determine the anthelmintic resistance status in cattle naturally infected with gastrointestinal nematodes. The anthelmintics tested were levamisole phosphate (Ripercol, Fort Dodge), albendazole sulphoxide (Ricobendazole, Fort Dodge), ivermectin (Ivomec, Merial) and moxidectin (Cydectin, Fort Dodge), administered at the doses recommended by the manufacturers. From April 2002 to May 2004, 25 cattle farms were evaluated. On each farm, steers were divided into treatment and control (not treated) groups based on fecal egg counts (FEC). Between 7 and 10 days after the anthelmintics administration, fecal samples were collected from each animal for post-treatment FEC. Fecal cultures from each group were also prepared for larval identification. After treatment, mean FEC reduction (FECR) in treatment groups (compared with control groups) was assessed on each farm. FECR was lower than 90% on 23 farms after ivermectin treatment. On 19 farms, FECR of 100% was recorded following moxidectin treatment; on the remaining 6, FECR ranged from 90% to 97.2%. After albendazole treatment, FECR was higher than 90% on 20 farms and ranged from 47.4% to 84.6% on other 5. After levamisole treatment, FECR was higher than 90% on 23 farms and equal to 47.4% and 73.7% on other 2 farms. Results indicated the presence of resistant Cooperia spp. and Haemonchus spp., especially to ivermectin; on some farms, resistance to albendazole and levamisole was also observed.

A case of poly-parasitism involving a trematode and four different nematodes in a migrant from Bihar

Reported is a case of seven-year-old, migrant from Bihar state, infested with Fasciolopsis buski Strongyloides stercoralis Ascaris lumbricoides, Trichuris trichiura and Ankylostoma duodenale in feces. Patient responded to treatment with piperazine, thiabendazole and albendazole, the importance of considering multiple and non-endemicparasite infestations in migrant of poor socio-economic background is emphasized.

Dairy goat production and the importance of gastrointestinal strongyle parasitism

In recent years, demand for goat products has increased in both developing and developed countries. Goat production (particularly dairy), however, is negatively affected by several factors, including infectious and parasitic diseases. Among the latter, gastrointestinal strongyle infection remains one of the main constraints to dairy goat production. In this mini-review, we emphasize the negative influence of these parasites, associated with subclinical production losses and depressive impacts upon long-term animal productivity, as well as the scarcity of studies on this topic. Finally, the necessity of reducing the use of anthelminthics and thus minimizing residues in food and the environment is stressed.

The effects of short-term feeding of fresh cassava (Manihot esculenta) foliage on gastrointestinal nematode parasite infections in goats in Cambodia

The antiparasitic effect of cassava (Manihot esculenta Crantz) was tested in goats artificially infected with gastrointestinal parasitic nematodes. Each experimental group consisted of 6 pen-fed goats kept on a slatted floor. The treatments compared were: 1) controls fed grass only, 2) cassava replaced grass for 3 weeks from the commencement of larval dosing period, and 3) cassava replaced grass for 3 weeks after the worm infection was patent. A total of 2000 mixed-species infective nematode larvae (L3) were administered to each goat in four doses of 500 L3/day, commencing 5 weeks after removal of previously acquired infections with ivermectin. The faecal egg counts (FEC) reduced in both cassava fed groups during the time of feeding, compared to the controls. Although, FEC increased differently with time (P < 0.05), total adult worm burdens at slaughter (week 15) were not different between the treatment groups. No differences in live weight gain, or packed cell volume, between treatments were found. Whilst these results show limited evidence of an anthelmintic effect of cassava in the diet, they do suggest that feeding, or supplementation, of cassava over an extended period may prove beneficial.

Subtilisin-like proteases in nematodes

Cleavage by subtilisin-like proteases (subtilases) is an essential step in post-translational processing of proteins found in organisms ranging from yeast to mammals. Our knowledge of the diversity of this protease family in nematodes is aided by the rapid increase in sequence information, especially from the Brugia malayi genome project. Genetic studies of the subtilases in Caenorhabitis elegans give valuable insight into the biological function of these proteases in other nematode species. In this review, we focus on the subtilases in filarial nematodes as well as other parasitic and free-living nematodes in comparison to what is known in C. elegans. Topics to be addressed include expansion and diversity of the subtilase gene family during evolution, enhanced complexity created by alternative RNA splicing, molecular and biochemical characterization of the different subtilases and the challenges of designing subtilase-specific inhibitors for parasitic nematodes.

Control of gastrointestinal nematodes with copper oxide wire particles in a flock of lactating Polypay ewes and offspring in Iowa, USA

Copper oxide wire particles (COWP) have been used to reduce infection of Haemonchus contortus in hair breed lambs in southeastern USA without signs of copper toxicity. However, copper sensitivity among breeds and regions varies. The objective was to determine the effectiveness and safety of COWP in lactating Polypay ewes and their offspring grazing alfalfa/bluegrass pasture in a rotational grazing system. Mature Polypay ewes were administered 0, 0.5, 1, or 2 g (n=8 or 9/dose) COWP approximately 60 days after lambing in mid-July 2005. Their offspring were administered 0 (n=6), 0.5 or 0.75 g (n=9), 1 or 2 g (n=6) COWP 2 weeks later in late July. The primary gastrointestinal nematode was H. contortus (70%). Between Days 7 and 35, FEC were greater in 0 and 0.5 g COWP groups compared with ewes administered 2 g COWP (COWP x day, P<0.004). PCV decreased in all groups of ewes between Days 0 and 21 (day, P<0.001). Aspartate aminotransferase (AST) activity, a measure of liver copper levels, and body weight was similar among groups of ewes. FEC decreased within 7 days in COWP-treated compared with untreated lambs and remained low throughout experiment (COWP x day, P<0.05). PCV increased in COWP-treated lambs between Days 7 and 35 and decreased in untreated lambs between Days 0 and 21 (COWP x day, P<0.009). AST activity was similar among groups of lambs. Administration of 2 g COWP to ewes prevented a rise in FEC, but a dose of 0.5 g was ineffective as an anthelmintic. Administration of all doses of COWP to lambs decreased FEC and increased PCV compared to untreated lambs. There were no signs of copper toxicity in ewes or lambs. Alternative suppression of H. contortus infections may be necessary in ewes, but COWP was effective in H. contortus management for lambs.

Combining the effects of supplementary feeding and copper oxide needles for the control of gastrointestinal nematodes in browsing goats

The aim was to assess the benefits obtained from combining supplementary feeding and copper needles (COWP), compared to the use of both approaches independently, for the control of gastrointestinal nematode (GIN) infections in browsing kids. Forty-four nematode free Criollo kids were exposed to natural parasite infection. The kids were divided into six experimental groups: not treated, supplemented (NT-S), not treated, not supplemented (NT-NS), moxidectin treated, supplemented (M-S), moxidectin treated not supplemented (M-NS), copper treated, supplemented (COWP-S) and copper treated, non-supplemented (COWP-NS). Copper treated groups received Copinox (2 g capsules) on day 0 and on day 60 of the trial. Moxidectin treated groups received Cydectin (0.2 mg/kg of body weight s.c.) every 28 days. Three of the groups received individual supplementation (100 g of feed/day fresh basis; 74% sorghum: 26% soybean meal; NT-S, M-S and COWP-S) and the other three groups were not supplemented (NT-NS, M-NS and COWP-NS). Animals browsed native vegetation (6.5 h/day) during the wet season (154 days). Kids were weighed every 14 days to determine live weight gain (LWG) and blood and faecal samples were obtained to determine packed cell volume (PCV), haemoglobin (Hb), peripheral eosinophil counts (PEC) and faecal egg counts (FEC). At the end of the trial, four kids of each group were euthanatized (six kids in each COWP treated group). Worm burdens, female worm lengths and prolificacy were determined. Liver samples were used to determine copper concentration and were stained with haematoxylin-eosin to determine microscopic lesions. Animals receiving the combination of supplementary feeding and COWP improved their LWG, PCV and Hb to similar levels of animals with suppressive AH treatment. This was not the case when COWP was used without supplementation. Liver copper concentration in COWP treated groups increased significantly especially in the COWP-NS kids but this was not associated with liver lesions or clinical signs. Post-mortem Haemonchus contortus and Trichostrongylus colubriformis worm counts had a tendency to be reduced in the different groups (66-35% reduction) compared to NT-NS group at the end of the trial (P>0.05). Also, COWP treatment and/or supplementation reduced female worm length of T. colubriformis and prolificacy of H. contortus and T. colubriformis. This study, confirmed the value of nutritional supplementation in the control of GIN in growing kids. The use of COWP in addition to supplementation had a limited contribution on the kids' resilience against GIN. This may be due to the reduced infection of H. contortus during this trial.

The effect of an indirect anthelmintic treatment on parasites and breeding success of free-living pheasantsPhasianus colchicus

In Great Britain free-living common pheasantsPhasianus colchicusare often managed at high densities owing to their popularity as a quarry species. They are prone to infection by a range of parasite species includingHeterakis gallinarum,Capillariaspp. andSyngamus trachea. In 1995 the efficacy of an indirect anthelmintic technique for controlling parasitic worm burdens of pheasants was determined in a pilot study on a shooting estate in the south of England. Between 2000 and 2003 a large-scale field experiment was conducted on nine estates in eastern England to determine the effect of the technique on parasite burden and pheasant breeding success. In the absence of anthelmintic treatment worm burdens increased rapidly through March and April, whereas birds given anthelmintic-treated grain had lower worm burdens during the same period. The breeding success of pheasants was significantly higher on plots provided with anthelmintic treatment, although no long-term increases in population densities were observed. The burdens of the most common parasiteH. gallinarumwere significantly lower in pheasants from treatment plots six weeks after the anthelmintic treatment had ceased, but spring treatment did not influence parasite burden in the following winter.

How effective is pre-release nematode control in farm-reared red-legged partridges Alectoris rufa?

Game bird farming is associated with high parasite levels that reduce farm productivity, reduce survival after releasing, and may pose a health risk for natural populations. The efficacy of albendazole (orally, 20 mg kg− 1) was evaluated in farmed red-legged partridges naturally infected with the nematodes Aonchotheca caudinflata and Heterakis gallinarum. In treated birds body condition improved, nematode egg deposition was reduced and the proportion of gravid A. caudinflata females was reduced, but not the overall worm burdens. Albendazole was found to be 36.8% and 17.1% effective against A. caudinflata and H. gallinarum, respectively. These results indicate that the anthelmintic treatment used normally in Spanish partridge farms is not effective enough to avoid the introduction of parasites into the field after release.

Anthelmintic resistance in cattle nematode in the western Pampeana Region of Argentina

During the past three years there have been several reports of cattle anthelmintic resistance (AR) in Argentina. Twenty-five cattle herds in the west fattening area of the Pampeana Region were surveyed to assess the prevalence of AR and the species of nematode involved. The survey involved fattening and cow-calf systems with a mean of 6760 bovines. Resistance was determined in vivo by a faecal egg count reduction test (FECRT). Efficacies from the World Association for the Advancement of Veterinary Parasitology (WAAVP) formula were compared with those obtained from the Abbott formula. Sixty 6-12-month-old calves were selected from each property and divided into four groups, namely, IVM (ivermectin, 0.2mg/kg), BZD (fenbendazole, 5mg/kg or albendazole 7.5mg/kg), LVM (levamisole, 7.5mg/kg) and Control (untreated group). Nematode larvae were identified by four pooled faecal cultures for each group. Cooperia and Ostertagia were the predominant nematode larvae in pre-treatment cultures. The mean FECRT efficacies for IVM, BZD and LVM were 81.0+/-21%, 93.3+/-8% and 97.6+/-4%, respectively. AR was detected in 16 (64%) herds. IVM resistance was present in 15 herds and BZD resistance in eight herds (32%). Resistance to both ivermectin and fenbendazole was present in seven herds. LVM resistance was not detected. Cooperia was the predominant post-treatment nematode in all the herds with IVM resistance. In one herd with IVM resistance, Ostertagia counts were slightly increased over pretreatment counts. Ostertagia was the prevalent post-treatment genera in herds with BZD resistance. A high level of resistance to ivermectin was recorded in this fattening region of Argentina. Also several herds with resistance to benzimidazole were observed. These results show the importance of AR in Argentinian cattle production. High correlation between WAAVP and Abbott formulae was observed. However, under some uncertain diagnosis, both formulae could be applied as complementary to help result interpretations.

Repeated treatment faecal egg counts to identify gastrointestinal nematode resistance in a context of low-level infection of sheep on farms in eastern Algeria

The efficacy of benzimidazoles and ivermectin was tested in 14 pilot farms in eastern Algeria. Resistance was detected in strongyle nematodes against benzimidazoles (five farms) and ivermectin (one farm). The main genera in the region were resistant: Teladorsagia, Trichostrongylus, Marshallagia and Nematodirus. The evaluations based on FECRT (faecal egg count reduction tests) were not always consistent due to the low-level of infection, and we developed a simplified, repeated treatment strategy to investigate resistance. The results obtained with repeated treatment faecal egg counts match globally those obtained with conventional faecal egg count reduction tests. This simplified, repeated treatment method should be investigated further since it is quicker, and this could make it possible to test larger farm samplings.

Diffuse unilateral subacute neuroretinitis: report of a case from the Indian subcontinent and the importance of immediate photocoagulation

PURPOSE

To report a case of DUSN from the Indian subcontinent and emphasize the importance of immediate photocoagulation.

METHOD

Review of case record.

RESULT

The referring ophthalmologist had photographed the subretinal worm but had not undertaken laser photocoagulation. On presentation to us the patient had features typical of DUSN but no worm could be detected despite repeated examinations. Failure to localize the worm at subsequent examinations resulted in only partial recovery of vision.

CONCLUSION

Whenever the nematode is detected, immediate laser photocoagulation of the worm is necessary as the migratory worm may be difficult to identify later on. This is necessary to prevent the otherwise natural decline in vision.

Comparative efficacy of different anthelmintics against fenbendazole-resistant nematodes of pashmina goats

A trial using albendazole, albendazole plus rafoxanide combination, ivermectin and doramectin was conducted in Pashmina goats having history of fenbendazole resistance to Haemonchus spp. and maintained at high altitude (>2350 m above sea level). Day 0 infection level was variable in different groups of animals and their larval cultures indicated Haemonchus, Trichostrongylus, Ostertagia and Oesophagostomum spp. infection, in addition to Nematodirus spp. as observed in egg counts. Efficacy of drugs was calculated on day 14 post treatment by faecal egg count reduction test (FECRT). Albendazole was least effective (14%) followed by its combination with rafoxanide (54%). However, ivermectin and doramectin were 96% and 94% effective against gastrointestinal nematodes of Pashmina goats. It was concluded that use of albendazole and its combination with rafoxanide are ineffective in controlling the nematodes of goats at this farm; hence, future use must be avoided. However, regular monitoring of the efficacy of ivermectin and doramectin is needed.

Gastrointestinal nematodes of small ruminants: life cycle, anthelmintics, and diagnosis

Strongylid gastrointestinal nematodes are an important cause of disease and economic loss in small ruminants. These parasites are particularly important in the eastern United States where the bloodsucking parasite Haemonchus contortus is the predominant species. Sheep and goats are infected with gastrointestinal nematodes while grazing and the biology of the infective larvae on the pastures is important in planning effective control programs. Fecal egg counts can be used to monitor control programs and drug efficacy and evaluate levels of pasture contamination.

Anthelmintic activity of Spigelia anthelmia extract against gastrointestinal nematodes of sheep

In vitro (larval development assay) and in vivo studies were conducted to determine possible direct anthelmintic effect of ethanolic and aqueous extracts of Spigelia anthelmia towards different ovine gastrointestinal nematodes. The effect of extracts on development and survival of infective larvae stage (L(3)) was assessed. Best-fit LC(50) values were computed by global model of non-linear regression curve fitting (95% confidence interval). Therapeutic efficacy of the ethanolic extracts administered orally at a dose rate of 125, 250, and 500 mg/kg, relative to a non-medicated control group of sheep harbouring naturally acquired infection of gastrointestinal nematodes, was evaluated in vivo.The presence of S. anthelmia extracts in the cultures decreased the survival of L(3) larvae. The LC(50) of aqueous extract (0.714 mg/ml) differ significantly from the LC(50) of the ethanolic extract (0.628 mg/ml) against the strongyles (p < 0.05, paired t-test). Faecal egg counts on day 12 after treatment showed that the extract is effective, relative to control (one-way analysis of variance [ANOVA], Dunnett's multiple comparison test) at 500 mg/kg against Strongyloides spp. (p < 0.01), 250 mg/kg against Oesophagostomum spp., Trichuris spp. (p < 0.05), and 125 mg/kg against Haemonchus spp. and Trichostrongylus spp. (p < 0.01). The effect of the doses is significant in all cases, the day after treatment is also extremely significant in most cases, whereas interaction between dose and day after treatment is significant (two-way ANOVA). S. anthelmia extract could, therefore, find application in the control of helminth in livestock, by the ethnoveterinary medicine approach.

Field evaluation of the efficacy and the safety of a combination of oxantel/pyrantel/praziquantel in the treatment of naturally acquired gastrointestinal nematode and/or cestode infestations in dogs in Europe

In five multicentre field trials, the efficacy and safety of a combination of oxantel/pyrantel/praziquantel (Dolpac), Vetoquinol SA) in the treatment of naturally acquired gastrointestinal nematode and/or cestode infestation in dogs was evaluated in northern and southern Europe. Forty-eight investigators from France, Belgium, Germany, Italy and Spain enrolled 329 dogs to be treated with the tested combination; 235 of these dogs complied with the inclusion criteria of the protocol and had a tested helminth identified on Day 0. A pooled analysis was performed on each of the following helminth species: Toxocara canis, Ancylostoma caninum, Toxascaris leonina, Trichuris vulpis, Uncinaria stenocephala, Taenia spp. and Dipylidium caninum, which were isolated on Day 0. The main efficacy criterion was the egg per gram (epg) percent reduction of the nematodes and the absence of proglottids and or eggs for the cestodes. After treatment, dogs were examined on Day 7, Day 14 and Day 21. The efficacy of the combination against Toxocara canis was 99.1%, 98.8% and 98.9% on Day 7, Day 14 and Day 21, respectively. At the same occasions the efficacy was, respectively, 99.2%, 99.2% and 99.3% against Ancylostoma caninum, 97.3%, 97.2% and 98.4% against Trichuris vulpis, 98.4%, 98.8% and 98.8% against Uncinaria stenocephala, 98.9%, 99.5% and 99.9% against Toxascaris leonina, 97.1%, 100% and 100% against Dipylidium caninum and 100% against Taenia spp.

Comparative study of the quality and efficacy of originator and generic albendazole for mass treatment of soil-transmitted nematode infections in Nepal

The quality and efficacy of two locally manufactured generic albendazole (ABZ) products (Curex and Royal Drug) used for deworming children in Nepal since 1999 were tested against the originator product (GlaxoSmithKline (GSK)). The study included disintegration and dissolution testing according to the Indian Pharmacopoeia (IP) and the United States Pharmacopeia (USP), respectively, as well as a randomised controlled clinical trial comparing cure rates (CR) and egg reduction rates (ERR) for Ascaris lumbricoides, Trichuris trichiura and hookworm infections. Stool samples from 1277 children were examined before and 21 days after treatment. For A. lumbricoides, GSK (97.0%) and Royal Drug (95.0%) ABZ achieved significantly higher CRs than Curex ABZ (82.6%); however, all products achieved ERRs >90%. For T. trichiura, Curex ABZ showed significantly lower ERRs (63.2%). For hookworms, GSK ABZ performed significantly better (CR 74.3%, ERR 87.1%) than Royal Drug ABZ (CR 53.3%, ERR 80.8%) and Curex ABZ (CR 50.7%, ERR 73.1%). Only the GSK product passed both disintegration and dissolution tests according to the IP and USP. Both generic products failed the dissolution tests. Curex ABZ showed poor disintegration. Despite its lower efficacy, the cheaper Curex product achieved good results in controlling morbidity due to soil-transmitted helminth infections. This study shows that the cost effectiveness of drugs used in mass deworming campaigns should not be inferred on the basis of a single quality testing parameter.

Clearance of a dermal Huffmanela sp. in a sandbar shark (Carcharhinus plumbeus) using levamisole

A wild-caught captive sandbar shark Carcharhinus plumbeus developed a contiguous network of darkly pigmented linear tracks that progressed from the snout to the ventral cervical region. Microscopic examination of a skin scraping revealed nematode eggs of the genus Huffmanela, a group of histozoic nematodes that is known to parasitize requiem sharks and marine and freshwater teleosts. The fresh eggs were darkly pigmented with bipolar plugs, contained a larva, and measured 73.3 to 86.4 by 39.0 to 47.4 microm (n = 10). Formalin-fixed and paraffin-embedded eggs were significantly smaller (Wilcoxon rank sums test, p < 0.005), measuring 70.5 to 78.9 by 33.6 to 41.3 microm (n = 13). These measurements do not correlate with previously reported species of Huffmanela. Serial treatment with levamisole (10 mg kg(-1), intramuscular [i.m.]) cleared the egg tracks within 21 d, with no recurrence or apparent complications.

Parasitic pulmonary eosinophilia

Parasitic infections, although common in tropical and subtropical regions, are prevalent worldwide because of changing immigration patterns and in international travel. The burden of worm infection is enormous and the intensity of infection is usually high among the poor and in immunocompromised individuals. Pulmonary eosinophilia occurs in almost all metazoan infections. In the Western world, the most common infections are caused by Strongyloides, Ascaris, Toxocara, and Ancylostoma species. Most of the nematodes multiply within the human host and cause pulmonary eosinophilia during larval migration through the lungs. Despite larval migration through the lungs, there is usually no permanent lung damage. The result is an increased number of eosinophils in the airways or lung parenchyma with or without peripheral eosinophilia. Löffler's syndrome, visceral larva migrans, and tropical pulmonary eosinophilia are the most common infections that cause pulmonary eosinophilia. The most serious parasitic eosinophilic lung disease is tropical pulmonary eosinophilia, a disorder caused by the filarial worms Wuchereria bancrofti and Brugia malayi, in which cases have typically been reported to masquerade acute or refractory bronchial asthma. Increasing awareness, newer diagnostic techniques, preventative measures, and antiparasitic drugs are important in reducing the worldwide morbidity and mortality from parasitic helminths and protozoa. This review focuses on common and some uncommon causes of pulmonary parasitic eosinophilia and their manifestations, diagnosis, and management.

Avermectin-resistance in gastrointestinal nematodes of Boer goats and Dorper sheep in Switzerland

Anthelmintic resistance in gastrointestinal nematodes among small ruminants is widespread in South Africa and Dorper sheep and Boer goats have been imported into Switzerland from this country on a number of occasions. Therefore, this study aimed to investigate the occurrence of avermectin (AVM) resistant gastrointestinal nematodes (GIN) in these breeds in Switzerland. A total of 24 Boer goat farms and 12 Dorper sheep farms participated in the study. According to the faecal egg count reduction test (FECRT) AVM-resistant GIN populations were confirmed in 7 of the 24 Boer goat farms and suspected in a further 8 farms. Likewise AVM-resistance was confirmed in 2 of 12 Dorper sheep farms and suspected in a further 6 farms. Haemonchus contortus and Trichostrongylus spp. were the dominant resistant species according to larval cultures. In the farms with detected AVM-resistance the animals were additionally treated with levamisole after natural reinfection. With the exception of one farm with a 'close-to cutoff-result' the FECRT gave no indication for resistance against levamisole. The results indicate that AVM-resistance is widespread in Swiss small ruminant farms keeping Boer goats and Dorper sheep. The common tradition of grazing animals from different farms on prealpine and alpine pastures could favour the spread of resistant populations within the country.

Human gastrointestinal nematode infections: are new control methods required?

Gastrointestinal (GI) nematode infections affect 50% of the human population worldwide, and cause great morbidity as well as hundreds of thousands of deaths. Despite modern medical practices, the proportion of the population infected with GI nematodes is not falling. This is due to a number of factors, the most important being the lack of good healthcare, sanitation and health education in many developing countries. A relatively new problem is the development of resistance to the small number of drugs available to treat GI nematode infections. Here we review the most important parasitic GI nematodes and the methods available to control them. In addition, we discuss the current status of new anthelmintic treatments, particularly the plant cysteine proteinases from various sources of latex-bearing plants and fruits.

Alternatives to anthelmintics for the control of nematodes in livestock

Efficient and welfare-friendly livestock production demands the control of nematode infection. Current control measures rely upon anthelmintic treatment but are threatened by the widespread evolution of drug-resistance in parasite populations. Several methods have been advocated to control nematodes without relying on effective anthelmintics. These include grazing management, biological control, nutritional supplementation, vaccination, and genetic approaches. Each method has its advantages and disadvantages. There are several grazing management schemes that can reduce the severity of infection but they are insufficient on their own to control infection. Biological control includes the use of predatory fungi to control nematode populations and the use of pasture species that can reduce the intensity of infection. Fungi can control nematodes but the current requirement for daily feeding means that this approach will be most useful for animals that are handled daily. Feeding supplementary protein can control nematode infection. The method is simple but can be expensive and may not be cost-effective for some marginal enterprises. Genetic approaches include the use of resistant breeds and selective breeding. Some breeds will thrive in conditions that kill animals from other breeds but substitution of resistant breeds is not always feasible. Selective breeding is effective and inexpensive but requires a high level of expertise. The most appropriate method or set of methods to minimize the adverse consequences of nematode infection may vary among farms.

Assessment of anthelmintic resistance in nematode parasites of sheep and goats owned by smallholder farmers in eastern Ethiopia

The anthelmintic resistance status was investigated of nematode parasites of sheep and goats owned by smallholder farmers in communities that received breeding stock from a source where a high level of anthelmintic resistance has been reported. The investigation used the faecal egg count reduction technique, whereby suitable animals within each of eight separate communities were pooled to achieve the numbers required to conduct separate tests for both sheep and goats. Anthelmintics tested were albendazole (ABZ), tetramisole (TET), a combination (ABZ + TET) and ivermectin (IVM), at the manufacturers' recommended dose rates. Results showed that there was no evidence of anthelmintic resistance in nematode parasites of either sheep an goats in any community. This indicates that dilution of resistant parasites imported with introduced breeding stock, and the low selection pressure imposed by the smallholder farmers themselves, has prevented anthelmintic resistance from emerging in nematode parasites of small ruminants in these communities.

Anthelmintic activity of Swertia chirata against gastrointestinal nematodes of sheep

This paper describes in vitro and in vivo anthelmintic activities of Swertia chirata. In vitro studies revealed that at 25 mg/ml (P>/=0.05) the crude aqueous (CAE) and methanolic extracts (CME) of S. chirata whole plant showed an anthelmintic effect on live Haemonchus contortus. Moreover, in the in vivo study, the whole plant of S. chirata administered as crude powder (CP), CAE and CME at the dose of 3 g/kg to sheep naturally infected with mixed species of gastrointestinal nematodes, showed a significant reduction in egg per gram of faeces.

Chinese herbal medicine Yin-Chen-Extract as an adjunct to anthelmintic albendazole used against Angiostrongylus cantonensis-induced eosinophilic meningitis or meningoencephalitis

The effects of albendazole and Yin-Chen-Extract co-therapy on Angiostrongylus cantonensis-induced eosinophilic meningitis in BALB/c mice were evaluated. Assay indicators for the therapeutic effect include worm recovery, histopathological score of the fourth ventricle, tissue-type plasminogen activator, urokinase-type plasminogen activator, matrix metalloproteinase-9, cerebrospinal fluid total protein, leukocyte counts, and proinflammatory cytokines. As a result, albendazole and Yin-Chen-Extract co-therapy significantly decreased (P < 0.05) these factors. Although Yin-Chen-Extract may possess pharmacologic activities beneficial to the inhibition of parasite-induced inflammation, many of these hypothetical benefits await scientific testing and confirmation before application. This study suggests that the combination of Yin-Chen-Extract and albendazole has synergistic effects in managing eosinophilic meningitis or eosinophilic meningoencephalitis.

Endoparasite Control

The gastrointestinal nematodes are considered to be the most important group of internal parasites. Gastrointestinal parasitism is a major constraint to animal health, productivity, and profitability in grazing livestock production systems. The clinical manifestations of infection may range from no apparent effect to death. Despite years of research, assessment of production losses in many regions of the United States and of the potential impact of gastrointestinal nematode control remains to be determined.

In vivo anthelmintic activity of ginger against gastrointestinal nematodes of sheep

This paper describes the anthelmintic activity of Zingiber officinale Roscoe (family Zingiberaceae) rhizome, commonly known as ginger, to justify its traditional use in veterinary medicine. Crude powder (CP) and crude aqueous extract (CAE) of dried ginger (1-3 g/kg) were administered to sheep naturally infected with mixed species of gastrointestinal nematodes. Both CP and CAE exhibited a dose- and a time-dependent anthelmintic effect with respective maximum reduction of 25.6% and 66.6% in eggs per gram (EPG) of faeces on day 10 of post-treatment. Levamisole (7.5 mg/kg), a standard anthelmintic agent, exhibited 99.2% reduction in EPG. This study shows that ginger possesses in vivo anthelmintic activity in sheep thus justifying the age-old traditional use of this plant in helminth infestation.

The early drug selection of nematodes to anthelmintics: stochastic transmission and population in refuge

We have developed an individual-based model to reflect the complexity of the early phase of drug resistance selection in a nematode/sheep model. The infection process consists of the stochastic ingestion of infective larvae spatially aggregated in clumps. Each clump corresponds to infective larvae, which are the offspring of the mature nematodes from a given sheep. We studied the dynamics of the parasitic population and the frequency of the recessive resistance alleles during selection by anthelmintic treatments. The interaction between genetic and demographic processes illustrated the trade-off between the control of the infection and the delay of resistance selection. We confirmed the importance of the number of treatments and their timing. The same treatment frequency may result in different outcomes on resistance selection in relation to the size of the refuge (infective larvae on pasture). Treatment applied during the summer (when the mortality of infective larvae on pasture was high), may lead to a rapid selection of drug resistance and a lack of control of sheep and pasture contamination. We showed that higher stocking rates were also a force in promoting the resistance allele selection.

Control of gastrointestinal nematodes in goats on pastures in South Africa using nematophagous fungi Duddingtonia flagrans and selective anthelmintic treatments

The effectiveness of selective anthelmintic treatments and use of nematophagous fungi Duddingtonia flagrans in reducing levels of gastrointestinal nematodes in goats was investigated at Onderstepoort, South Africa. Nineteen (19) naturally infected indigenous male goats, aged 10 months, were separated into four groups and grazed in separate previously ungrazed paddocks for two worm seasons (February 2002-March 2003). Two groups of goats were fed D. flagrans chlamydospores daily and two groups did not receive fungi. The FAMACHA system was used to determine which goats required anthelmintic treatments. Twice as many goats in the no-fungi fed group required treatments as compared with the fungi fed group. Mean FAMACHA scores in the no-fungi fed group were higher during most of the sampling occasions compared to the group fed fungi, but the difference was not significant. The group-mean faecal egg counts and PCV% were comparable between the two treatment groups throughout the study. Haemonchus was the predominant parasite genus in composite group faecal cultures. Group-mean body weights and body condition scores were higher for the no-fungi fed group from May 2002 up to the end of the study, though statistical differences were not significant. Mean worm burdens indicated that the most abundant species infecting animals were Haemonchus contortus and Trichostrongylus spp. and were higher in the fungi fed group. More animals required individual anthelmintic treatments in the no-fungi fed group. The requirement for extra treatments in the no-fungi fed group must, however, be considered against the financial cost of the fungi, the requirement of daily feeding of the fungi, the lower performance and higher worm burdens in the fungi fed group.

Efficacy of selamectin against mites (Myobia musculi, Mycoptes musculinus and Radfordia ensifera) and nematodes (Aspiculuris tetraptera and Syphacia obvelata) in mice

The effects of selamectin were studied in mice naturally infected with the mites Myobia musculi, Myoceptes musculinus and Radfordia ensifera and with the oxyurid nematodes Aspiculuris tetraptera and Syphacia obvelata. The mice were divided into three treated and three control groups (n=9). Selamectin in the range 10-12.4 mg/kg was applied topically to the skin in a single spot at the base of the neck in front of the scapulae. The mice of treated and control groups were necropsied on the 4th, 7th and 21st day after the treatment. While selamectin was 100% effective in removing M. musculi, M. musculinus and R. ensifera by the seventh day, its effect against S. obvelata and A. tetraptera was 36.7% and 49.2%, respectively on the 21st day.

Serratospiculosis in falcons from Kuwait: incidence, pathogenicity and treatment with melarsomine and ivermectin

The aims of this study were to determine the incidence of the filarial avian nematode Serratospiculum seurati in falcons from Kuwait, report clinical signs and find an effective therapy. Naturally occurring S. seurati infestation was diagnosed in 149 (8.7%) out of 1,706 captive falcons examined between May 2003 and April 2005, and 140 of these were treated with melarsomine at dosage of 0.25 mg/kg injected intramuscularly for two days, and ivermectin, injected once at the dose of 1 mg/kg, 10 days later. Infestation was reportedly symptomatic in 107 (71.8%) and non-symptomatic in 42 (28.2%) falcons. Signs reported more often were dyspnoea (58.8%), reduced speed and strength in flight (56%), weight loss (38.3%), anorexia/poor appetite (22.4%) and lethargy (16.8%). After administration of melarsomine, signs disappeared within 1-10 days in symptomatic birds and improvement of flight performances was noted in non-symptomatic birds. Dead adult parasites were ejected in 22 cases. Embryonated eggs were not detected in coproscopic checks made 10 and 40 days after the end of therapy, in association with lasting clinical remission. The main conclusion is that Serratospiculum seurati is overall pathogenic for birds of prey in the Middle East and that melarsomine + ivermectin can be an effective protocol of therapy eliminating both clinical signs and parasites.

Efficacy of short-term feeding of sulla (Hedysarum coronarium) to young goats against a mixed burden of gastrointestinal nematodes

The aim was to investigate the efficacy of feeding sulla to young goats (<6 months of age) against a naturally acquired infection of gastrointestinal nematodes. Eleven goats were removed from the field, housed and were randomly divided into two treatment groups. Group 1 (n = 5) was fed a diet comprising lucerne-based pellets and aged hay. Group 2 (n = 6) were fed a diet of only sulla offered ad lib. The sulla contained 2.6% free condensed tannins (CT), 1.8% protein-bound CT and 0.1% fibre-bound CT. Goats in Gp 2 ate the sulla very readily from the first day. The goats were fed these diets for 10 days, then killed and total worm counts obtained. The arithmetic mean worm counts (in parentheses) for Gp 1 and Gp 2, respectively, were Teladorsagia circumcincta (5792, 5690), Trichostrongylus colubriformis (272, 262), T. vitrinus (1060, 1804) and Trichuris spp. (32, 30). There were no significant differences (p > 0.05) between any of these treatments. Short-term feeding of sulla had no effect on mixed burdens of gastrointestinal nematodes.

Molecular diagnosis of anthelmintic resistance

Conventional and real time polymerase chain reaction-based tests have been developed for the diagnosis of anthelmintic resistance (AR) in populations of several small and large ruminant as well as horse gastro-intestinal nematode species. To date, molecular markers that correlate well with AR are available only for the detection of benzimidazole resistance. Recently, however, a single nucleotide polymorphism was found in vitro to be of functional relevance for reduced drug efficacy to macrocylic lactones. The focus of the present review, therefore, is the molecular mechanism of action of these two drug classes and potential applications of this knowledge to the diagnosis of AR. It is argued that a prerequisite for future molecular diagnosis will be tests providing reliable and exact quantification of resistance related alleles in DNA extracted from representative pools of parasites.

[Effect of a novel drug--enteric coated tribendimidine in the treatment of intestinal nematode infections]

OBJECTIVE

To study the therapeutic effect and possible adverse effects of tribendimidine enteric coated tablets in the treatment of infections due to hookworms, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis.

METHODS

According to the standard clinical trial design and protocol, persons infected with hookworms, Ascaris lumbricoides, Trichuris trichiura, or Enterobius vermicularis respectively, were treated with tribendimidine enteric coated tablets in four counties of Guangdong and Jiangsu Provinces, albendazole was used as control.

RESULTS

For hookworm infection, the curative rate (eggs negative in the faeces) were 89.5% (85/95) and 70.6% (60/85) with tribendimidine (400 mg) and albendazole(400 mg) respectively; for Ascaris infection, 97.4% (114/117) and 98.9% (91/92) with tribendimidine(300 mg) and albendazole(400 mg) respectively; for Trichuris infection, 33.3% (25/75) and 56.1% (23/41) with tribendimidine(400 mg/day for 3 days) and albendazole(400 mg/day for 3 days) respectively; for Enterobius infection in children, 74.1% (60/81) and 93.0% (40/43) with tribendimidine(200 mg) and albendazole(200 mg) respectively. No considerable side effect was found.

CONCLUSION

Tribendimidine is highly active in the treatment of hookworm, Ascaris lumbricoides infections, free of major adverse effect and easy to administer. It is more effective than albendazole for the infection of Necator americanus.

Influence of protein supplementation on the resistance and resilience on young hair sheep naturally infected with gastrointestinal nematodes during rainy and dry seasons

Thirty, 4-month-old entire Santa Ines lambs were grazed on an Andropogon gayanus pasture, during a 34-week period (rainy season weeks 0-20 and dry season weeks 21-34) and allocated in two treatment groups (n = 15) each with different protein supplementation: high protein (HP-19% CP) and low protein (LP-11% CP). These were subdivided into those receiving anthelmintic treatment (c) (n = 7) and without anthelmintic treatment (i) (n = 8). The objective was to evaluate the effects of supplementation with protein on resistance and resilience to natural helminth infection of hair breed lambs. Lamb weight, blood collection and faecal egg counts (FEC) were carried out monthly. The lambs were slaughtered after 34 weeks, when worm burdens, worm length and eosinophil cell counts were taken. The sheep on treatments HPc and HPi were heavier in live weight than those from LPi and LPc (P < 0.05) at the end of the rainy period. The HPc group finished heavier (P < 0.05) than the other groups in the dry season, which had no significant differences between them. The predominant species of nematode found was T. colubriformis followed by H. contortus, Trichuris globulosa and Moniezia expansa. Animals on HPi had lower FEC than LPi (P < 0.05). The number of worms was lower for both HP groups (P < 0.05) with worm length shorter in the HPc group (P < 0.05) compared with all other groups. The number of eosinophils was higher in animals in the LPi group, which also showed anaemia and lower plasma urea at the end of the dry season. Diet supplementation with high protein was able to improve resilience and resistance to natural infection by endoparasites during the rainy season. In the dry season there was a decrease in both of these traits, which were intimately linked to the quality of available forage under tropical conditions.

Anthelmintic resistance of nematode parasites of small ruminants in eastern Ethiopia: Exploitation of refugia to restore anthelmintic efficacy

Faecal egg count reduction tests (FECRT) were conducted in May 2003 to determine the efficacy of anthelmintics used for treatment against nematode parasites in separately managed sheep and goat flocks at Alemaya University in eastern Ethiopia. These tests revealed high levels of anthelmintic resistance to albendazole, tetramisole, the combination of these two drugs, and to ivermectin in the goat flock (predominantly infected by Haemonchus contortus and Trichostrongylus spp.), whereas all drugs were highly efficacious in the sheep flock. A second FECRT confirmed these observations. Following this, a new management system was implemented on the goat flock for a period of 9 months (January-September 2004) in an attempt to restore the anthelmintic efficacy. This involved a combination of measures: eliminating the existing parasite infections in the goats, exclusion from the traditional goat pastures, and introducing communal grazing of the goats with the university sheep flock and livestock owned by neighbouring small-holder farmers. A second series of FECRTs (Tests 3 and 4) conducted 7 months after this change in management, showed high levels of efficacy to all three drugs (albendazole, tetramisole and ivermectin) in the goat flock. This is the first field study to demonstrate that anthelmintic efficacy in the control of nematode parasites of small ruminants can be restored by exploiting refugia.