Medical Parasitology Revision Notes OmpathStudy

VECTOR CONTROL METHODS 1. Physical/Mechanical Screened windows/doors, mosquito nets, draining pools, clearing long grass, emptying containers 2. Biological Toxorhynchites larvae — prey on Anopheles/Culex/Aedes larvae Gambusia affinis (fish) — eats larvae Bacillus thuringiensis (Bt), Bacillus sphaericus — bacterial larvicides Other natural predators 3. Genetic Engineering Sterile male technique Refractory vectors — gene modification blocks pathogen development → change in target site 4. Chemical — LD50 classification: 1–50 = extremely toxic, 50–500 = moderately toxic Class Mechanism Examples Notes --- --- --- --- Chlorinated hydrocarbons Nerve poison, disrupts Na⁺ channels, lipid-soluble DDT, Dieldrin, Endrin Mostly banned — persistent, bioaccumulates Organophosphates (OP) Blocks cholinesterase Malathion, Chlorpyrifos, Parathion, Diazinon, Dimethoate Less persistent than organochlorines Carbamates Bind acetylcholinesterase (reversible) Carbaryl, Propoxur, Bendiocarb Lower toxicity, better than OPs on chronic exposure Pyrethroids Bind voltage-gated Na⁺ channels, delay inactivation Permethrin (ITNs/LLINs), Deltamethrin Rapid "knockdown" effect, safe outdoors Insect Growth Regulators (IGRs) Block chitin/sugar biosynthesis Pyriproxyfen, Diflubenzuron Formamidines Mimic octopamine, disordered neuronal excitation Amitraz, Chlordimeform Effective on resistant insects, mites/ticks Avermectins Inhibit nerve impulse transmission Abamectin Narrow spectrum; also anti-nematode Neonicotinoids Mimic nicotine, systemic + contact Imidacloprid Targets sucking insects Miticides Anti-mite Bromopropylate, Cyhexatin, Tetradifon Application types: contact poison, fumigant, systemic, stomach poison, respiratory poison --- KEY TERMINOLOGY Anthropophilic (human blood) vs Zoophilic (animal blood) Endophagic (feeds indoors) vs Exophagic (feeds outdoors) Endophilic (rests indoors) vs Exophilic (rests outdoors) Autogenous (eggs w/o blood meal) vs Anautogenous (needs blood meal) Parthenogenesis — asexual, no fertilization needed --- MOSQUITOES (Culicidae) Anopheles Species: gambiae complex (supervector), funestus, arabiensis (zoophilic), melas, stephensi (supervector, Asia-origin, recently in Africa — heat/arid-tolerant, unlike native African species) Anthropophilic, endophagic, endophilic Life cycle: holometabolous (complete); optimal 25°C, 78% humidity Eggs: laid singly, float on surface Larvae: 4 instars (L1–L4), lie parallel to surface, breathe via body-side spiracles, feeding stage Pupa: comma-shaped, resting stage, emerges 2–3 days Adults rest at 45° angle ; males bushy/plumose antennae, females smooth/pilose Only females bite (anautogenous); males feed on sugar only; parthenogenesis possible Vector: Malaria (Plasmodium) Control: larvicides, Toxorhynchites (biological), refractory index/endosymbionts (genetic), draining, nets, IRS, trans-ovarian light traps, screening, cutting grass Culex Species: C. quinquefasciatus Exophagic, exophilic; feeds 3pm–6pm (nocturnal), diurnal feeding ~10am Breeds: contaminated water (sewage, drains) Eggs: laid simultaneously as a raft , float Larvae: siphon breathing, hang at 45° angle (unlike Anopheles' parallel posture) Host detection: eyes + olfactory cues Vector: Wuchereria bancrofti (filariasis), Rift Valley fever, West Nile virus — transovarial transmission (adults emerge already infected) Control: sanitation/sewage systems, insecticide on larval habitats (7–10 days spray), light traps, wire mesh Aedes Species: aegypti, albopictus Black with white spots, painful biters "Container breeders" — clean containers, tires, flower vases Bimodal biting: early morning + late evening; both sexes bite during oviposition Vector: Dengue, Chikungunya, Zika, Yellow fever, O'nyong-nyong, Japanese encephalitis; Rift Valley fever (mechanical); transovarial transmission of arboviruses Control: remove vegetation/containers, straighten rivers to increase flow, Bt insecticide, light traps, larvivorous fish --- SANDFLIES (Psychodidae: Phlebotominae) Old World: Phlebotomus (4 subgenera) New World: Lutzomyia (e.g. L. umbratilis, Brazil) Sergentomyia — zoophilic Distribution: worldwide — Mediterranean, Indian subcontinent, Sub-Saharan Africa, Asia, Central/South America Breed: cracks, holes in ground, termite mound bases, chicken coops, animal burrows, rubbish heaps; need high humidity, can't survive desiccation Weak fliers, short mouthparts, bite exposed skin; anthropophilic; some autogenous Bimodal biting: early morning + early evening Vector: L. donovani → visceral leishmaniasis L. tropica → cutaneous leishmaniasis (Old World) L. braziliensis complex → mucocutaneous leishmaniasis Bartonella bacilliformis → Carrion's disease Sandfly fever virus (Phlebovirus) Control: remove termite mounds, DEET/Picaridin, protective clothing, time outdoor activity, spray cracks/burrows, destroy rodent reservoirs --- BITING MIDGES (Ceratopogonidae) — "no-see-ums" Genera: Leptoconops (tropics), Culicoides (worldwide) Breed in wet mud/sand