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COH603: Public Health Biology

Class 4: Wednesday, June 12 2013. COH603: Public Health Biology. Plans for Today. Malaria HPV HPV paper Break Midterm Exam. Zoonosis and Vectors. “An infection or infectious disease transmissible under natural conditions from vertebrate animals to humans.”

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COH603: Public Health Biology

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  1. Class 4: Wednesday, June 12 2013 COH603: Public Health Biology

  2. Plans for Today • Malaria • HPV • HPV paper • Break • Midterm Exam

  3. Zoonosis and Vectors “An infection or infectious disease transmissible under natural conditions from vertebrate animals to humans.” • A disease vector is a living agent that transfers a pathogen from one organism to another. • Examples of Vector: • Various species of rodents (rats and mice) • Arthropods (mosquitoes, ticks, sand flies) • The vector can transport the pathogen from an infected individual or its wastes to a susceptible individual or its food or immediate surroundings

  4. Vector-Borne Diseases

  5. Infectious Agent of Malaria • 4 human types: • Plasmodium falciparum • Most deadly • Plasmodium vivax • Plasmodium ovale • Plasmodium malariae • subsaharan • Mixed infections not infrequent

  6. Risk of Malaria Worldwide

  7. Malaria • Affects at least 200,000,000 people per year • Kills 4 – 5 people each minute • 1,000,000 children in Africa die each year • Major cause of mortality/morbidity in children aged 1 - 4

  8. Malaria in the U.S. • 1,000 cases annually • Primarily imported (exposure can be brief), although can be indigenous • Transfusions • Deaths secondary to improper chemoprophylaxis, delayed presentation to care, misdiagnosis

  9. Anopheles mosquito bite

  10. Mosquito Life Cycle • Require standing or slow moving water • Eggs laid on surface of water (viable for months of desiccation) • Larvae (1 week), Pupae (3 days) • Males prefer flowers, females prefer blood • Zoophilic, anthrophilic or can switch

  11. Malaria life cycle

  12. Malaria Life Cycle

  13. Amplification of Malaria Infection 1 Sporozoite 5,000 – 10,000 Merozoites from the liver hypnozoites Each merozoite develops into 10 – 20 merozoites in RBCs (schizonts)

  14. Blood Smear Thick Smear: Diagnosis of Malaria

  15. P. falciparum blood stages

  16. P. vivaxblood stages

  17. Merozoites leaving RBC

  18. Normal RBC, RBC with PF

  19. Importance in Differentiating Malaria Species Four species: P. falciparum, vivax, malariae, ovale Early treatment important and dependent on species • complications with P. falciparum • risk of chloroquine resistance with P. falciparum • dormant liver stage with P. vivax and P. ovale

  20. Symptoms and Signs of Malaria • Cold Stage: Chills, headache, vomiting, nausea • Hot Stage: Fever and tachycardia • Sweating Stage: Defervescence, fatigue • Physical Exam: Fever, pale, may have splenomegaly

  21. P. vivax fever cycle

  22. Malaria: Prevention Prevention: Personal protection and chemoprophylaxis • Mefloquine • Doxycycline • Primaquine

  23. Malaria: Treatment • P. vivax, ovale, malariae: Chloroquine and Primaquine • P. falciparum:Mefloquine, Quinine and TCN, Fansidar

  24. Malaria in U.S. Current Issues • Misdiagnosis in ERs • Appropriate preventive measures • Drug resistance

  25. Malaria Vaccine Challenges • Immunity is specific – species, strain, and stage • Strategies for vaccine developments • Sub-unit molecular products • Target essential functions at each stage

  26. Worldwide Malaria PreventionCurrent Issues • Vector control - difficult & expensive • Treatment of symptomatic disease • Access to drugs • Effective regimens • Compliance • Rx and prevention of anemia • Prevention of severe/fatal outcomes • Facilitation immunity

  27. Resurgence of Malaria • Parasites resist drugs • Mosquitoes resist insecticides • People not cooperate with program • Governments reduce program funding • Human migration • Global warming

  28. Controlling Malaria • During mid-20th century, malaria was all but eliminated in many countries due to the use of pesticides, particularly DDT. • Known to be harmful to wildlife, outdoor spraying of DDT was discontinued in many developed countries. • Mosquitoes resurged • Some countries now permit the spraying of DDT inside of homes.

  29. Mosquito Resistance • Mosquito resistance to insecticides has been detected in 64 countries around the world • in all major malaria vector species and all four existing classes of insecticides. • Endemic countries are urged to develop and implement comprehensive insecticide resistance management strategies and ensure timely entomological and resistance monitoring.

  30. Malaria Data and Statistics • 2012 WHO Malaria Health Report • There were about 219 million cases of malaria in 2010 and an estimated 660 000 deaths. • Africa is the most affected continent: about 90% of all malaria deaths occur there.

  31. Data and Statistics • Between 2000 and 2010, malaria mortality rates fell by 26% around the world. • In the WHO African Region the decrease was 33%. • an estimated 1.1 million malaria deaths were averted globally • aresult of a scale-up of interventions.

  32. Funding for Malaria Prevention • Available funding for malaria prevention and control is far below the resources required to reach global malaria targets. • An estimated $ 5.1 billion is needed every year between 2011 and 2020 to achieve universal access to malaria interventions. • In 2011, only $ 2.3 billion was available

  33. Disease Burden • Malaria remains inextricably linked with poverty. • The highest malaria mortality rates are being seen in countries that have the highest rates of extreme poverty

  34. Malaria Surveillance • Malaria surveillance systems detect only around 10% of the estimated global number of cases. • In 41 countries around the world, it is not possible to make a reliable assessment of malaria trends due to incompleteness or inconsistency of reporting over time.

  35. Three Steps to Control Malaria • Biological • Introduce mosquito-eating fish into ponds • Use sentinel chickens • Largely experimental • Environmental • Elimination of larval habitats (Ex: drain standing water). Most likely method to be effective in the long term • Repair window screens as an extra protection, bednets • Wear repellents and protective clothing • Chemical Control: • Larvicides may be used to kill immature aquatic stages • Ultra-low volume fumigation ineffective against adult mosquitoes • Mosquitoes may have resistance to commercial aerosol sprays

  36. Rice paddies in northern Thailand

  37. Thailand – Burma Border

  38. Map indicating areas targeted in Round 2 and Round 7 Project areas • Malaria transmission areas (A1, A2) • A1 areas: 460 villages in 28 provinces (417,535 population) • A2 areas: 2,885 villages in 43 provinces (2,068,501 population) • Total project area A1 + A2: 2,486,036 population

  39. Motorcycling to village

  40. Walking to village

  41. Taking blood slides in village

  42. Thick film technique

  43. Thin film technique

  44. Recording blood slides in village

  45. Malaria office

  46. Giemsa staining blood slides

  47. Examining blood slides

  48. Malaria clinic

  49. Antimalaria medicine

  50. Catching mosquito larvae

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