Animals Humans Epizootic Epidemic Enzoonotic Endemic Some terminology Zoonosis: infectious disease that can be transmitted from other animals to humans Reservoir host: host in which an infectious disease is maintained -> (often) no ill effect on the animal host -> enzoonotic Amplifying host: a host in which infectious agents multiply to high concentrations -> animal hosts get ill -> epizootic 1"Increase in Arboviruses in last 20 years Reasons are complex and not fully understood -> mostly demographic and societal changes population growth urbanization deforestation -> complacency in vector control -> globalization increase in human migration trade in exotic animals (e.g. West Nile Virus) 2"West Nile Virus 20% will develop West Nile Fever fever, headache, tiredness, body aches (can last several weeks) Severe disease: West Nile Encephalitis West Nile Meningitis, West Nile Meningoencephalitis headache coma high fever tremors stupor convulsions disorientation paralysis Death People > 50 are at highest risk Symptoms: 80% asymptomatic (1/150) Flavivirus 3"2009: 335 West Nile Encephalitis cases: 30 deaths 2010: 601 Neuroinvasive cases, 45 deaths 4"West Nile Transmission Cycle Bridge vector Bridge Vector: a vector that is responsible for transmitting disease from animals to humans. 5"Eastern"Equine"Encephali5s""Western"Equine"Encephali5s""St"Louis"Encephali5s""LaCrosse""Encephali5s""""""4;5%"develop"Encephali5s"13%"develop"encephali5s"?" ?"33%"fatality"rate" 3%"fatality"rate" 5;30%"fatality"rate" <1%"fatality"rate"2;3"neuro;invasive"cases/year"16""neuro;invasive"cases/year""116"neuro;invasive"cases/year"80;100"neuro;invasive"""cases/year"Swamps"(+rural)" Rural"areas" Rural"+"urban" Wooded"areas"Birds" Birds"(+Rabbits)" Birds" chipmunks/squirrels"6"Mosquitoes and the diseases they transmit V Lymphatic Filariasis Public Health Entomology 7"The"Five"Kingdoms.Malaria Arbovirusses Nematodes (roundworms) Virusses are not organisms 8"Animal.Phyla.9"Nematoda 80,000 species described (500,000 estimated total) 15,000 are parasitic (e.g. Hookworm, Pinworm) Most free-living nematodes are microscopic, though a few parasitic forms can grow to over a meter in length (typically as parasites of very large animals such as whales) Largest found in humans -> 1 meter in length Free-living nematodes have colonized every habitat on earth Ascaris lumbricoides Intestinal parasite (non-vector borne) 10"11"12"Filarial Worms Family Onchocercidae: 34 genera Transmitted by all major groups of blood-feeding insects Superfamily Filarioidea Medical Importance for humans: Wuchereria, Brugia, Onchocerca, and Loa Lymphatic filariasis Brugia malayi Wuchereria bancrofti 13"Three species of filarial worms cause lymphatic filariasis Wuchereria bancrofti Brugia malayi Brugia timori 91 % of cases (no animal host) 9% of cases (zoonotic diseases with minor animal reservoir hosts) 1.2 billion people at risk 120 million cases of lymphatic filariasis (83 countries) 40 million people have serious illness 80 million people have hidden internal damage 14"Wuchereria bancrofti life cycle Life cycle is the same for B. malayi and B. timori 15"Wuchereria bancrofti life cycle • Mosquitoes ingest small microfilariae from blood – Move from gut to flight muscles & mature into infective larvae (3rd instars = L3) – L3 larvae (1.5mm) migrate to mosquito head & enter humans via bite – L3 larvae mature slowly into adults in lymphatic system – Adults mate & microfilariae produced – Microfilariae adapted for mosquito uptake (can’t mature in humans) Infective (L3) larvae 16"Filarial worm crawling out of mosquito proboscis 17"Distribution of Wuchereria bancrofti, Brugia malayi and Brugia timori Endemic in Charleston, SC until early 20th century 1/3 Africa, 1/3 India, 1/3 rest of Asia 18"History Mentuhotep II (4000 BP) Earliest description in ancient Egypt Ancient Greeks and Romans produced detailed descriptions. 16th century: European explorers described Elephantiasis 1863: worms were described from blood and lymph of patients 1877: Manson discovered that Wuchereria bancrofti is transmitted by Culex Beginning of Medical Entomology 19"Wuchereri bancrofti vectors Genera Culex, Aedes, Anopheles, Culex vectors: Culex quinquefasciatus is an ubiquitous vector and abundant in tropical and subtropical countries. Anopheles vectors: The genus Anopheles is important in the transmission of W .bancrofti in Africa, Southern Asia and the island of New Guinea. Aedes vectors: Aedes species such as A.polynesiensis, A.samoanus are mainly distributed in Samoa and French Polynesia and A.poecilius in the Phillipines 20"Brugia malayi vectors Aedes and Mansonia Mansonia require vegetation for larval stage -> clearing vegetation is effective control method. Reservoir hosts 21"Microfilaria migration 22"Different subtypes Nocturnal periodic: microfilaria only detectable at night Nocturnal subperiodic: microfilaria detectable but higher density at night Diurnal subperiodic: microfilaria detectable but lower density at night 23"Periodicity is correlated with vector behavior and vertebrate host Also, nocturnal periodic B. malayi is strictly human pathogen Nocturnal subperiodic B. malayi is zoonosis In the case nocturnal periodicity -> vector feeds at night In subperiodic forms -> multiple vectors with different feeding pattern are present (enough microfilaria are present during low period to infect mosquitoes) 24"The lymphatic system Main functions: 1 collect and return fluid to the circulatory system 2 part of immune system (produces lymphocytes) 3 absorbs lipids from the intestine 25"Symptoms 3 phases Phase 1 Many individuals have microfilaria in blood, but have few or no symptoms (asymptomatic microfilaremia) These individuals are the primary reservoir Some individuals have swollen lymph nodes May progress to phase 2 and 3 (but not always) (the three species cause similar disease) 26"Acute inflammatory lymphatic disease (adenolymphangitis) -> episodic pain and tenderness of the lymph nodes -> filarial fevers -> deep abscesses may form at the site on inflammation -> secondary bacteria infection (microfilaria are usually not observed in these patients) Phase 2 (Acute) This is caused by dead worms 27"lymphathic pathology: (blockage of