Resistance Watch
A proposed field map for helminth drug-resistance signals, monitoring projects and evidence gaps.
The problem
Helminth control in humans and animals depends heavily on repeated use of a small number of drug classes. Veterinary parasitology already shows what can happen when drug pressure is high and alternatives are limited: resistance can become widespread across benzimidazoles, macrocyclic lactones, levamisole and newer classes. In human helminth programmes, resistance is not yet established as a broad public-health problem, but reduced efficacy and suboptimal response signals make monitoring urgent.
Resistance Watch would track where field efficacy, genetic markers, phenotypic assays and programme data suggest changing drug performance. It treats human and veterinary evidence together, because the same drug classes, mechanisms and parasite populations often cross the human, livestock and wildlife boundary.
Current monitoring initiatives
- STARWORMS — international network focused on soil-transmitted helminths, benzimidazole efficacy and anthelmintic-resistance monitoring.
- RESIST — project investigating whether praziquantel resistance contributes to persistent urogenital schistosomiasis in Pemba, Zanzibar.
- WHO Working Group on Monitoring of NTD Drug Efficacy — coordinates review and guidance for efficacy monitoring in large-scale deworming programmes.
- WHO efficacy monitoring guidance — technical guidance for monitoring praziquantel, albendazole and mebendazole efficacy.
- COMBAR — European COST action on combatting anthelmintic resistance in ruminant helminths.
- Yale hookworm resistance project — work on benzimidazole resistance markers in Necator americanus.
Integrated drug-resistance watchlist
RAG key: Green broadly effective with limited confirmed resistance; Amber effective but under surveillance or class-level threat; Red widespread resistance or serious field efficacy threat in at least one major use setting.
| Drug / class | Human, livestock or One Health use | Resistance picture | Mechanism / marker | References |
|---|---|---|---|---|
| Benzimidazoles RedAlbendazole, mebendazole, fenbendazole, oxfendazole | Human STHs, echinococcosis and neurocysticercosis; livestock and companion-animal nematodes; oxfendazole development for human helminths. | Albendazole and mebendazole remain essential for humans, but efficacy is weak for Trichuris and benzimidazole resistance is widespread in livestock nematodes. This is one of the clearest One Health warning signals. | β-tubulin mutations, especially F167Y, E198A/L and F200Y, reduce benzimidazole binding to parasite microtubules. | CDC STH treatment; STH efficacy meta-analysis; resistance review; MSD veterinary overview. |
| Diethylcarbamazine GreenDEC; antifilarial | Lymphatic filariasis in settings without onchocerciasis; part of IDA combinations with ivermectin and albendazole. | No dominant resistance crisis comparable to veterinary nematodes, but use is constrained by safety in onchocerciasis/loiasis co-endemic areas. | Mechanism is incompletely resolved; host immune effects and parasite arachidonic-acid / surface biology have been proposed rather than a validated resistance marker. | WHO LF preventive chemotherapy; CDC filarial clinical care. |
| Doxycycline and anti-Wolbachia drugs GreenDoxycycline, flubentylosin and related candidates | Macrofilaricidal strategy for onchocerciasis and lymphatic filariasis where regimens and safety constraints are feasible. | Not an anthelmintic resistance problem in the usual sense. Operational limits are pregnancy/children contraindications, regimen length and access. | Targets Wolbachia endosymbionts rather than worm neuromuscular or cytoskeletal targets. | anti-Wolbachia review; DNDi flubentylosin. |
| Emodepside GreenCyclooctadepsipeptide | Companion-animal nematodes; DNDi human-development candidate for onchocerciasis. | No widespread field-resistance crisis comparable to older veterinary classes, but resistance-aware deployment should be built in before broad use. | Latrophilin-like receptors and SLO-1/BK-channel signalling are core pharmacology; lab resistance can involve this pathway. | DNDi emodepside; emodepside pharmacology review. |
| Macrocyclic lactones RedIvermectin, moxidectin, doramectin, eprinomectin, abamectin, milbemycins | Human onchocerciasis, strongyloidiasis, lymphatic-filariasis combinations and scabies; livestock and companion-animal nematodes and ectoparasites. | Ivermectin and moxidectin remain very important in humans, but suboptimal response signals exist for onchocerciasis and macrocyclic-lactone resistance is widespread in livestock nematodes. | Likely polygenic. Candidate mechanisms include P-glycoprotein / ABC transporters, glutamate-gated chloride channel changes and broader neuronal or detoxification pathways. | Ghana onchocerciasis perspective; P-glycoprotein marker paper; FDA moxidectin approval; class review. |
| Monepantel RedAmino-acetonitrile derivative | Veterinary small-ruminant gastrointestinal nematodes, especially where older classes have failed. | Resistance emerged rapidly after introduction in some countries, showing that new classes can also be lost without stewardship. | Mutations or disruption in DEG-3-like nicotinic receptor pathway genes, especially mptl-1 / ACR-23-like targets. | resistance review; COMBAR. |
| Niclosamide GreenTapeworm drug; globally used where available | Intestinal cestodes including Taenia species; less central where praziquantel/albendazole dominate. | Resistance is not a dominant field-control issue, but availability and replacement by other drugs limit modern surveillance. | Uncouples oxidative phosphorylation / mitochondrial energy metabolism; no routine field resistance marker. | NCBI anthelmintic agents; CDC taeniasis treatment context. |
| Nicotinic agonists RedPyrantel, morantel, levamisole, tribendimidine | Pyrantel is used in humans and animals; levamisole/morantel are major veterinary drugs; tribendimidine is used regionally for human helminths. | No dominant human pyrantel resistance crisis, but veterinary resistance is well documented and class biology is directly relevant to human neuromuscular-target discovery. | Altered nicotinic acetylcholine receptor subunits, receptor expression and neuromuscular sensitivity; tribendimidine has related nicotinic receptor pharmacology. | CDC STH treatment; tribendimidine review; resistance review. |
| Nitazoxanide GreenFDA-approved antiparasitic; limited helminth use | Primarily protozoal infections; sometimes discussed for intestinal helminths such as hymenolepiasis where alternatives are limited. | Not a central helminth-control drug and no major helminth resistance signal. | Interferes with anaerobic energy metabolism; helminth-specific resistance markers are not established. | NCBI anthelmintic agents. |
| Other fasciolicides AmberClosantel, rafoxanide, oxyclozanide, nitroxynil, clorsulon | Mainly veterinary fluke control; potential relevance where livestock reservoirs and human fascioliasis overlap. | Important alternatives to triclabendazole, but reduced efficacy and resistance reports are increasing; mechanisms are less well mapped than for nematode drug classes. | Mechanisms vary by drug and remain incompletely resolved; altered uptake/exposure, metabolism, detoxification and target-level effects are plausible. | fasciolicide resistance review. |
| Oxamniquine RedLegacy schistosomiasis drug | Historically used for S. mansoni; now largely superseded by praziquantel. | Clinically limited and species-specific, but important because its resistance mechanism is unusually well understood. | Loss or alteration of schistosome sulfotransferase SmSULT prevents activation of the prodrug. | SmSULT resistance mechanism; oxamniquine mechanism review. |
| Praziquantel AmberHuman and veterinary flatworm drug | Schistosomiasis, cestodes and many trematode infections; also used in veterinary and aquaculture settings. | Still the cornerstone for schistosomiasis and tapeworm treatment, but reliance on one drug, persistent hotspots and experimental resistance make active surveillance essential. | TRPMPZQ is a key mechanistic target/marker candidate; resistance may also involve altered drug exposure, metabolism or efflux. | RESIST; PZQ mode/resistance review; PZQ resistance brief. |
| Triclabendazole RedHuman Egaten; veterinary liver-fluke drug | Fascioliasis in humans and livestock; uniquely important because it targets immature and adult Fasciola. | Critical drug, but confirmed Fasciola hepatica resistance is widespread in livestock and human treatment failures have been reported in endemic settings. | Not a simple β-tubulin story. Evidence points to a major resistance locus plus altered drug exposure, metabolism, efflux and stress-response pathways. | FDA Egaten approval; major resistance locus; fasciolicide resistance review. |
What Resistance Watch would do
- Track field efficacy studies, reduced-efficacy reports and suboptimal response signals.
- Connect drug class, parasite species, geography, treatment history and evidence quality.
- Link phenotypic assays with genetic markers such as β-tubulin and TRPMPZQ candidates.
- Bring veterinary resistance lessons into human helminth drug-development planning.
- Support resistance-aware combinations, rotation strategies and deployment models for new medicines.