Parasites Of Livestock Research Articles

Species‐rich dung beetle communities buffer ecosystem services in perturbed agro‐ecosystems

SummaryMany studies document high levels of functional redundancy in ecosystems, suggesting that species extinctions will not be detrimental to ecosystem functions and services. However, apparently redundant taxa may prove critical for sustaining ecosystem functions and services in the context of environmental perturbations.Dung beetles (Coleoptera:Scarabaeidae) provide a valuable ecosystem service in temperate agro‐ecosystems by increasing rates of dung decomposition and nutrient cycling. However, there is concern that these services may be negatively affected by changes in species richness and composition due to changes in pasture management and negative effects of anthelmintics used to control livestock parasites.We used a mesocosm experiment to investigate the functional importance of dung beetle species richness in a system perturbed by the anthelmintic, ivermectin. We varied dung beetle species richness within three functional groups in factorial combination with ivermectin treatment.In the short term (1–4 weeks), multi‐species dung beetle assemblages achieved higher decomposition rates than monocultures, but only in ivermectin‐treated dung. Varying species‐specific sensitivities to ivermectin meant that species‐rich assemblages sustained ecosystem functioning in the context of this anthropogenic perturbation.Over the longer term (36 weeks), there was a significant, positive effect of species richness on dung decomposition in both ivermectin‐treated and untreated dung, underlining the functional importance of maintaining a species‐rich dung processing community even in the absence of perturbations to the system.Synthesis and applications. The interacting effects of dung beetle species richness and ivermectin highlight the importance of maintaining diverse assemblages in the face of anthropogenic perturbations and suggest that apparent functional redundancy of species in agro‐ecosystems should be interpreted cautiously. Furthermore, different farm management practices (e.g. pesticide use and fragmentation of habitats) may have consequences for ecosystem functions and services that exceed the effects of each when considered in isolation.

An Overview of the Components of AW-IPM Campaigns against the New World Screwworm.

The New World Screwworm, Cochliomyia hominivorax (Coquerel), is one of the most damaging parasites of livestock, causing millions of dollars in annual losses to producers. The fly is an obligate parasite of warm-blooded animals, including humans. After a successful 50-year eradication campaign, C. hominivorax has been eradicated from the USA, Mexico and Central America by an area-wide integrated pest management approach. Recently, Caribbean and South American countries have expressed an interest in this approach. Aiming to support forthcoming projects in these countries, this review describes the main technical components of past and ongoing AW-IPM campaigns against C. hominivorax.

Infection levels of gastrointestinal parasites in sheep and goats in Papua New Guinea

Gastrointestinal parasites of livestock cause diseases of important socio-economic concern worldwide. The present study investigated the prevalence of gastrointestinal parasites in sheep and goats in lowland and highland regions of Papua New Guinea (PNG). Faecal samples were collected from a total of 165 small ruminants (110 sheep and 55 goats) from February to April 2011. Analysis by a modified McMaster technique revealed that 128 animals (72% of sheep and 89% of goats) were infected with one or more species of gastrointestinal parasites. The gastrointestinal parasites found and their prevalences in sheep (S) and in goats (G) were as follows: strongyle 67.3% (S), 85.5% (G); Eimeria 17.3% (S), 16.4% (G); Strongyloides, 8.2% (S), 23.6% (G); Fasciola, 5.5% (S), 18.2% (G); Trichuris, 1.8% (S), 3.6% (G); and Nematodirus, 1.8% (S), 3.6% (G). Two additional genera were found in goats: Moniezia (9.1%) and Dictocaulus (3.6%). This is the first study to quantitatively examine the prevalence of gastrointestinal parasites in goats in PNG. The high rates of parasitism observed in the present study are likely to be associated with poor farming management practices, including lack of pasture recovery time, lack of parasite control measures and poor-quality feed.

Molecular epidemiological studies on animal trypanosomiases in Ghana

BackgroundAfrican trypanosomes are extracellular protozoan parasites that are transmitted between mammalian hosts by the bite of an infected tsetse fly. Human African Trypanosomiasis (HAT) or sleeping sickness is caused by Trypanosoma brucei rhodesiense or T. brucei gambiense, while African Animal Trypanosomiasis (AAT) is caused mainly by T. vivax, T. congolense, T. simiae,T. evansi and T. brucei brucei. Trypanosomiasis is of public health importance in humans and is also the major constraint for livestock productivity in sub-Saharan African countries. Scanty information exists about the trypanosomiasis status in Ghana especially regarding molecular epidemiology. Therefore, this study intended to apply molecular tools to identify and characterize trypanosomes in Ghana.MethodsA total of 219 tsetse flies, 248 pigs and 146 cattle blood samples were collected from Adidome and Koforidua regions in Ghana in 2010. Initial PCR assays were conducted using the internal transcribed spacer one (ITS1) of ribosomal DNA (rDNA) primers, which can detect most of the pathogenic trypanosome species and T. vivax-specific cathepsin L-like gene primers. In addition, species- or subgroup-specific PCRs were performed for T. b. rhodesiense, T. b. gambiense, T. evansi and three subgroups of T. congolense.ResultsThe overall prevalence of trypanosomes were 17.4% (38/219), 57.5% (84/146) and 28.6% (71/248) in tsetse flies, cattle and pigs, respectively. T. congolense subgroup-specific PCR revealed that T. congolense Savannah (52.6%) and T. congolense Forest (66.0%) were the endemic subgroups in Ghana with 18.6% being mixed infections. T. evansi was detected in a single tsetse fly. Human infective trypanosomes were not detected in the tested samples.ConclusionOur results showed that there is a high prevalence of parasites in both tsetse flies and livestock in the study areas in Ghana. This enhances the need to strengthen control policies and institute measures that help prevent the spread of the parasites.

Melanisation of Teladorsagia circumcincta larvae exposed to sunlight: A role for GTP-cyclohydrolase in nematode survival

Trichostrongylid nematode parasites of livestock inhabit two very different niches during their life-cycle; within the host and free-living in the environment. UV radiation plays a significant role in the survival of free-living, pre-parasitic nematode larvae, with different species exhibiting differing levels of sensitivity. In many eukaryotes, melanisation is a key protective mechanism against UV damage, however there is little information about this process in parasitic nematodes. Caenorhabditis elegans cat-4 mutants, which are deficient in the enzyme guanosine triphosphate-cyclohydrolase I (GTP-CH), have both depleted levels of melanin in their cuticles and an increased sensitivity to anthelmintic drugs. Some parasitic nematodes have very high levels of GTP-CH transcript in their pre-parasitic stages, suggesting an important role for this biopterin synthetic enzyme. Here, we show that the Tci-cat-4 gene, which encodes GTP-CH in Teladorsagia circumcincta, has a role in melanisation and is also capable of rescuing C. elegans cat-4 mutants. In addition, following exposure of T. circumcincta L3s to sunlight, there is a 32% increase in GTP-CH enzyme activity (P=0.019), and a 21% increase in levels of melanin (P=0.031) compared with unexposed larvae. These data suggest that one explanation for the high level of GTP-CH present in pre-parasitic stages of trichostrongylid nematodes is to facilitate melanisation in response to UV exposure.

Livestock Helminths in a Changing Climate: Approaches and Restrictions to Meaningful Predictions.

Simple SummaryParasitic helminths represent one of the most pervasive challenges to livestock, and their intensity and distribution will be influenced by climate change. There is a need for long-term predictions to identify potential risks and highlight opportunities for control. We explore the approaches to modelling future helminth risk to livestock under climate change. One of the limitations to model creation is the lack of purpose driven data collection. We also conclude that models need to include a broad view of the livestock system to generate meaningful predictions.Climate change is a driving force for livestock parasite risk. This is especially true for helminths including the nematodes Haemonchus contortus, Teladorsagia circumcincta, Nematodirus battus, and the trematode Fasciola hepatica, since survival and development of free-living stages is chiefly affected by temperature and moisture. The paucity of long term predictions of helminth risk under climate change has driven us to explore optimal modelling approaches and identify current bottlenecks to generating meaningful predictions. We classify approaches as correlative or mechanistic, exploring their strengths and limitations. Climate is one aspect of a complex system and, at the farm level, husbandry has a dominant influence on helminth transmission. Continuing environmental change will necessitate the adoption of mitigation and adaptation strategies in husbandry. Long term predictive models need to have the architecture to incorporate these changes. Ultimately, an optimal modelling approach is likely to combine mechanistic processes and physiological thresholds with correlative bioclimatic modelling, incorporating changes in livestock husbandry and disease control. Irrespective of approach, the principal limitation to parasite predictions is the availability of active surveillance data and empirical data on physiological responses to climate variables. By combining improved empirical data and refined models with a broad view of the livestock system, robust projections of helminth risk can be developed.

Introgression of Ivermectin Resistance Genes into a Susceptible Haemonchus contortus Strain by Multiple Backcrossing

Anthelmintic drug resistance in livestock parasites is already widespread and in recent years there has been an increasing level of anthelmintic drug selection pressure applied to parasitic nematode populations in humans leading to concerns regarding the emergence of resistance. However, most parasitic nematodes, particularly those of humans, are difficult experimental subjects making mechanistic studies of drug resistance extremely difficult. The small ruminant parasitic nematode Haemonchus contortus is a more amenable model system to study many aspects of parasite biology and investigate the basic mechanisms and genetics of anthelmintic drug resistance. Here we report the successful introgression of ivermectin resistance genes from two independent ivermectin resistant strains, MHco4(WRS) and MHco10(CAVR), into the susceptible genome reference strain MHco3(ISE) using a backcrossing approach. A panel of microsatellite markers were used to monitor the procedure. We demonstrated that after four rounds of backcrossing, worms that were phenotypically resistant to ivermectin had a similar genetic background to the susceptible reference strain based on the bulk genotyping with 18 microsatellite loci and individual genotyping with a sub-panel of 9 microsatellite loci. In addition, a single marker, Hcms8a20, showed evidence of genetic linkage to an ivermectin resistance-conferring locus providing a starting point for more detailed studies of this genomic region to identify the causal mutation(s). This work presents a novel genetic approach to study anthelmintic resistance and provides a “proof-of-concept” of the use of forward genetics in an important model strongylid parasite of relevance to human hookworms. The resulting strains provide valuable resources for candidate gene studies, whole genome approaches and for further genetic analysis to identify ivermectin resistance loci.

Parasitological survey of the Uruguayan populations of wild Pampas deer (Ozotoceros bezoarticus L. 1758)

The pampas deer (Ozotoceros bezoarticus) is one of the most endangered neotropical mammals in Uruguay. Although it has a wide geographic distribution in south-eastern South America (from 5°S to 41°S), the habitat required by this species has been greatly reduced by agriculture and urbanisation. The species decline was due to human activities, and currently two isolated populations survive. The parasitological load is a good indicator of the health of the species and the ecosystem. The objective of the present study was to survey and determine the parasitological composition of the two Uruguayan pampas deer populations. We quantified the coproparasite load, by analysing the effect of seasonality through the year, the micro-ecosystem environment, the topography and also the livestock of the paddock. The taxonomic assessment was based on adult individuals obtained from the post mortem necropsy examination in individuals found dead in the field. The genera of the endoparasites recorded through the morphological eggs, larvae and/or adults were Trichuris, Capillaria, Strongyloides, Fasciola, Paramphistomum, Moniezia, Haemonchus, Ostertagia, Trichostrongylus, Oesophagostomum and Coccidias ooquiste. Our results showed that the parasitological community in the pampas deer is strongly correlated with the environmental conditions, topology, micro-ecosystem and the land use, as well as the effect of the livestock load. Moreover, because we have diagnosed the same genera of helminths in domestic ruminants, we recommend balancing the carrying capacities of the field paddocks, and performing periodical surveys of the livestock parasite load that will be helpful in maintaining control at lower values.

Condensed Tannins Inhibit House Fly (Diptera: Muscidae) Development in Livestock Manure

Reducing chemical use for suppressing internal and external parasites of livestock is essential for protecting environmental health. Although plant condensed tannins are known to suppress gastro-intestinal parasites in small ruminants, no research on the effects of tannins on external arthropod populations such as the house fly, Musca domestica L., have been conducted. We examined the impact of plant material containing condensed tannins on house fly development. Prairie acacia (Acacia angustissima (Mill.), Kuntze variety hirta (Nutt.) B.L. Rob.) herbage, panicled tick-clover (Desmodium paniculatum (L.) DC.) herbage, and quebracho (Shinopsis balansae Engl.) extracts were introduced at rates of 1, 3 or 5% condensed tannins/kg beef cattle, dairy cattle, and goat manure, respectively. In a second experiment, we also introduce purified catechin at 1 or 3% of dairy manure dry matter and measured its impact on house fly development. For the house flies used in these experiments, the following was recorded: percent fly emergence (PFE), average daily gain (ADG), and average fly weight (AFW). No effects (P>0.05) in house fly development were measured in the caprine manure. Prairie acacia (20.9% condensed tannins) had no effect on house flies developing in either bovine manures. Tick clover (4.9% condensed tannins) had a negative effect on all three quantifiable variables of house fly development in the bovine manures, whereas quebracho extract (64.0% condensed tannins) at the 3 and 5% rate reduced fly emergence in beef manure and average daily gain in dairy manure. The application of purified catechin at 3%, but not 1%, reduced fly PFE, ADG, and AFW.

Novel approaches for the control of helminth parasites of livestock VI: Summary of discussions and conclusions

Gastrointestinal helminth parasites impact on livestock production systems throughout the world, and the use of anthelmintics to control this problem has lead to the inevitable development of populations of helminths resistant to these treatments. This, coupled with consumer desires for minimal chemical inputs into food and fibre production, has prompted research into non-chemical approaches to helminth control. Scientists of the “Novel Approaches to the Control of Helminth Parasites of Livestock” group met for the 6th time in August 2010 and this paper summarises that meeting. Six scientific sessions addressed current approaches and topics of interest through formal presentations and discussion of issues raised by the contributing authors. Close interaction between researchers and extension specialists during the meeting has contributed to enhanced prospects for field application of research outcomes in the future.

The Phosphobase Methylation Pathway in Caernorhabditis elegans: A New Route to Phospholipids in Animals.

Parasitic nematodes are a major cause of human health problems with an estimated 1 billion people infected worldwide by these organisms. Identifying biochemical targets that differ between the parasite and host species is essential for finding effective new anti-parasitic molecules. The free-living nematode Caenorhabditis elegans is a powerful model system for experiments in genetics and developmental biology needed to achieve this goal; however, in-depth understanding of metabolic processes in this organism is limited as it still contains unexplored biochemical pathways. Eukaryotes. including nematodes and humans, share many similar metabolic pathways, which makes specific targeting of nematode parasites challenging. Recent studies suggest that C. elegans and other nematodes may use a plant-like pathway as the major biosynthetic route to phosphatidylcholine. In this pathway, a pair of phosphoethanolamine methyltransferases (PMT) catalyze the sequential methylation of phosphoethanolamine to phosphocholine, which can be incorporated into phosphatidylcholine. RNAi experiments demonstrate that both PMT are required for normal growth and development of C. elegans. Because the PMT are highly conserved across nematode parasites of humans, livestock, and plants, as well as in protozoan parasites, understanding how these enzymes function and the identification of inhibitors will aid in the development of new anti-parasite compounds of potential medical, veterinary, and agricultural value.

Annotation of Two Large Contiguous Regions from the Haemonchus contortus Genome Using RNA-seq and Comparative Analysis with Caenorhabditis elegans

The genomes of numerous parasitic nematodes are currently being sequenced, but their complexity and size, together with high levels of intra-specific sequence variation and a lack of reference genomes, makes their assembly and annotation a challenging task. Haemonchus contortus is an economically significant parasite of livestock that is widely used for basic research as well as for vaccine development and drug discovery. It is one of many medically and economically important parasites within the strongylid nematode group. This group of parasites has the closest phylogenetic relationship with the model organism Caenorhabditis elegans, making comparative analysis a potentially powerful tool for genome annotation and functional studies. To investigate this hypothesis, we sequenced two contiguous fragments from the H. contortus genome and undertook detailed annotation and comparative analysis with C. elegans. The adult H. contortus transcriptome was sequenced using an Illumina platform and RNA-seq was used to annotate a 409 kb overlapping BAC tiling path relating to the X chromosome and a 181 kb BAC insert relating to chromosome I. In total, 40 genes and 12 putative transposable elements were identified. 97.5% of the annotated genes had detectable homologues in C. elegans of which 60% had putative orthologues, significantly higher than previous analyses based on EST analysis. Gene density appears to be less in H. contortus than in C. elegans, with annotated H. contortus genes being an average of two-to-three times larger than their putative C. elegans orthologues due to a greater intron number and size. Synteny appears high but gene order is generally poorly conserved, although areas of conserved microsynteny are apparent. C. elegans operons appear to be partially conserved in H. contortus. Our findings suggest that a combination of RNA-seq and comparative analysis with C. elegans is a powerful approach for the annotation and analysis of strongylid nematode genomes.

Improved PCR-RFLP for the Detection of Diminazene Resistance in Trypanosoma congolense under Field Conditions Using Filter Papers for Sample Storage

Improved PCR-RFLP for the Detection of Diminazene Resistance in Trypanosoma congolense under Field Conditions Using Filter Papers for Sample Storage

Dicrocoelium dendriticum: an emerging spurious infection in a geographic area with a high level of immigration.

Dicrocoelium dendriticum, commonly known as the Lancet liver fluke, is endemic in the Old World since prehistoric times (Le Bailly and Bouchet, 2010).

Reducing the future threat from (liver) fluke: realistic prospect or quixotic fantasy?

The liver fluke remains an economically significant parasite of livestock and is emerging as an important zoonotic infection of humans. The incidence of the disease has increased in the last few years, as a possible consequence of changes to the World's climate. Future predictions suggest that this trend is likely to continue. Allied to the changing pattern of disease, reports of resistance to triclabendazole (TCBZ) have appeared in the literature, although they do not all represent genuine cases of resistance. Nevertheless, any reports of resistance are a concern, because triclabendazole is the only drug that has high activity against the migratory and damaging juvenile stages of infection. How to deal with the twin problems (of increasing incidence and drug resistance) is the overall theme of the session on “Trematodes: Fasciola hepatica epidemiology and control” and of this review to introduce the session.Greater knowledge of fluke epidemiology and population genetics will highlight those regions where surveillance is most required and indicate how quickly resistant populations of fluke may arise. Models of disease risk are becoming increasingly sophisticated and precise, with more refined data analysis programmes and Geographic Information Systems (GIS) data. Recent improvements have been made in our understanding of the action of triclabendazole and the ways in which flukes have become resistant to it. While microtubules are the most likely target for drug action, tubulin mutations do not seem to be involved in the resistance mechanism. Rather, upregulation of drug uptake and metabolism processes appear to be more important and the data relating to them will be discussed. The information may help in the design of new treatment strategies or pinpoint potential molecular markers for monitoring fluke populations. Advances in the identification of novel targets for drugs and vaccines will be made by the various “-omics” technologies that are now being applied to Fasciola. A major area of concern in the current control of fasciolosis is the lack of reliable tests for the diagnosis of drug (TCBZ) resistance. This has led to inaccurate reports of resistance, which is hindering successful disease management, as farmers may be encouraged to switch to less effective drugs. Progress with the development of a number of new diagnostic tests will be reviewed.

Co-infection of Ornithodoros coriaceus with the relapsing fever spirochete, Borrelia coriaceae, and the agent of epizootic bovine abortion

The soft tick, Ornithodoros coriaceus (Koch) (Acari: Argasidae), is a common mammalian parasite of livestock in many arid regions of the western U.S.A. The tick is a known vector of the undescribed bacterial pathogen that causes epizootic bovine abortion (EBA), which results in late-term abortions in beef cattle and subsequent economic loss, which can be considerable, to producers. A second reported bacterial pathogen, Borrelia coriaceae, a member of the relapsing fever complex, has also been identified in this tick and was at one time hypothesized to be the aetiological agent of EBA. In order to test whether bacterial infections in ticks overlapped geographically and to determine the prevalence of co-infection in O. coriaceus populations, we used molecular methods to detect bacterial DNA from ticks collected from a wide variety of habitats in California, Nevada and Oregon. Of the 15 sites at which ticks tested positive for the agent of EBA (aoEBA), eight also contained ticks positive for Borrelia spp. by polymerase chain reaction assay. Additionally, two ticks were co-infected; both of these were collected from the same location. Univariate risk analysis indicated the presence of juniper-dominated habitat at the collection site and geographic location to be significantly associated with infection of the tick vector by either pathogen.

Genetic Mapping Identifies Novel Highly Protective Antigens for an Apicomplexan Parasite

Apicomplexan parasites are responsible for a myriad of diseases in humans and livestock; yet despite intensive effort, development of effective sub-unit vaccines remains a long-term goal. Antigenic complexity and our inability to identify protective antigens from the pool that induce response are serious challenges in the development of new vaccines. Using a combination of parasite genetics and selective barriers with population-based genetic fingerprinting, we have identified that immunity against the most important apicomplexan parasite of livestock (Eimeria spp.) was targeted against a few discrete regions of the genome. Herein we report the identification of six genomic regions and, within two of those loci, the identification of true protective antigens that confer immunity as sub-unit vaccines. The first of these is an Eimeria maxima homologue of apical membrane antigen-1 (AMA-1) and the second is a previously uncharacterised gene that we have termed ‘immune mapped protein-1’ (IMP-1). Significantly, homologues of the AMA-1 antigen are protective with a range of apicomplexan parasites including Plasmodium spp., which suggest that there may be some characteristic(s) of protective antigens shared across this diverse group of parasites. Interestingly, homologues of the IMP-1 antigen, which is protective against E. maxima infection, can be identified in Toxoplasma gondii and Neospora caninum. Overall, this study documents the discovery of novel protective antigens using a population-based genetic mapping approach allied with a protection-based screen of candidate genes. The identification of AMA-1 and IMP-1 represents a substantial step towards development of an effective anti-eimerian sub-unit vaccine and raises the possibility of identification of novel antigens for other apicomplexan parasites. Moreover, validation of the parasite genetics approach to identify effective antigens supports its adoption in other parasite systems where legitimate protective antigen identification is difficult.

Correlation between loss of efficacy of macrocyclic lactone heartworm anthelmintics and P-glycoprotein genotype

Macrocyclic lactone (ML) molecules have been used for heartworm control for more than 25 years. However, in recent years, there have been reports of loss of efficacy of ML heartworm preventatives against Dirofilaria immitis in some locations in the United States. Macrocyclic lactone resistance is a common problem in nematode parasites of livestock, and more recently, evidence of ivermectin resistance has been reported in the human filarial nematode Onchocerca volvulus. In this study, four D. immitis sample groups from the United States with different treatment histories were investigated for evidence of ML-driven genetic selection. DNA from individual adult worms and microfilariae was amplified by polymerase chain reaction to investigate a gene encoding a P-glycoprotein, a protein class known to be involved in ML pharmacology. A significant correlation of a GG–GG genotype with ivermectin response phenotype was found. Moreover, a significant loss of heterozygosity was found in a low responder group; loss of heterozygosity is commonly seen in loci when a population has been under selection. Further studies are required to confirm ML resistance in heartworm populations. However, the genetic changes observed in this study may be useful as a marker to monitor for ML resistance in D. immitis.

Prevalence of Liver Termatods and Hydatid Cyst in Livestock, Jiroft, Iran, 2001

Background: Hydatosis is one of the most and common parasitic disease and fasciola hepatica and gigantica has been considered as the most common of infection in herbivorous hepatobiliary system. The parasites not only cause to damage in animal husbandry industry but also can cause one of the parasitic diseases, which are common between human and livestock. This research was a cross-sectional study that was performed in all slaughtered livestock in order to determine the rate of infection to hydatid cyst and hepatic termatods in Jiroft , Iran, 2001. Methods: The liver of 358 goats, 316 calves, and 269 sheep were carefully examined to observe fasciola and the other organ for hydatid cyst. For analyzing the data, chi square test was performed using SPSS software. Results: The findings showed that prevalence of infection to the hydatid cyst was 8.5% in calves, 5.1 % in sheep and 7.8% in goats. The prevalence of fasciola hepatica was 0.9% in calves, 3.7% in sheep and 3 % in goats. Also, the prevalence of fasciola gigantic was 0.9% in calves, 1.6% in sheep and 2.8% in goats. The economical damages due to infected slaughtered livestock were 10,870,000 Rls. Conclusion: Because of the high prevalence of these parasites in slaughtered livestock in Jiroft, it is important to control them for prevention of economically and hygienically damages.

Ivermectin, 'wonder drug' from Japan: the human use perspective.

Discovered in the late-1970s, the pioneering drug ivermectin, a dihydro derivative of avermectin—originating solely from a single microorganism isolated at the Kitasato Intitute, Tokyo, Japan from Japanese soil—has had an immeasurably beneficial impact in improving the lives and welfare of billions of people throughout the world. Originally introduced as a veterinary drug, it kills a wide range of internal and external parasites in commercial livestock and companion animals. It was quickly discovered to be ideal in combating two of the world’s most devastating and disfiguring diseases which have plagued the world’s poor throughout the tropics for centuries. It is now being used free-of-charge as the sole tool in campaigns to eliminate both diseases globally. It has also been used to successfully overcome several other human diseases and new uses for it are continually being found. This paper looks in depth at the events surrounding ivermectin’s passage from being a huge success in Animal Health into its widespread use in humans, a development which has led many to describe it as a “wonder” drug.