Zoonotic and Vector-borne Diseases

Vector

". . . an insect or any living carrier that transports an infectious agent from an infected individual or its wastes to a susceptible individual or its food or immediate surroundings." Examples: Various mammal species Rodents Raccoons, bats, skunks, foxes, felines Arthropods Mosquitoes Ticks Sand flies Biting midges Horse flies and deer flies Lice Fleas

Lyme Disease

*A condition identified in 1977 when a cluster of arthritis cases occurred among children around the area of Lyme, Connecticut. *The causative agent for the disease is a bacterium known as Borrelia burgdorferi. *When infected deer ticks bite human beings the disease may be transmitted.

Malaria

*A disease found in more than 100 countries, with more than 40% of the world's population at risk *Endemic regions include Central and South America, Africa, India, Southeast Asia, the Middle East, and Oceania. *Annual death toll for malaria is up to 1 million persons. *Where malaria is found depends mainly on climatic factors such as temperature, humidity, and rainfalls. Malaria is transmitted in tropical and subtropical areas, where: Anopheles mosquitoes can survive and multiply. Malaria parasites can complete their growth cycle in the mosquitoes ("extrinsic incubation period"). Temperature is particularly critical. For example, at temperatures below 20°C (68°F), Plasmodium falciparum (which causes severe malaria) cannot complete its growth cycle in the Anopheles mosquito, and thus cannot be transmitted.

Zoonoses Examples and contributing factors

*Bacterial: Escherichia coli O157:H7 (hemolytic-uremic syndrome) Mass food processing technology allowing contamination of meat Lyme disease Habitat changes Decreased spp. diversity; fewer predators *Parasitic: Cryptosporidium and other pathogens Contaminated surface water, faulty water purification Non-conventional agent (prions?): Bovine spongiform encephalopathy Changes in rendering process Chronic wasting disease (deer, elk, etc.)? Unknown factors *Viral: >HIV/AIDS Bushmeat?; Human pop growth; Global travel >Hantaviruses >Ecological/environmental changes Increasing rodent contacts SARS coV; Hendra; Nipah; Ebola Env disruption; animal husbandry

Rocky Mountain Spotted Fever

*Caused by Rickettsia rickettsii bacteria *Most common rickettsial disease in U.S. *Fever, severe HA, nausea, vomiting, rash *Transmitted by the bite infected tick *Diagnosis: Tick bite history or exposure Signs/symptoms *Treatment: Doxycycline (adults and children) *Case fatality rate up to 25% among untreated patients

Abroviral (Encephalitis)

*Caused by a virus that produces an acute inflammation of: Sections of the brain Spinal cord Meninges *Among the etiologic agents are viruses associated with many forms of encephalitis, including: St. Louis encephalitis Western equine encephalitis Eastern equine encephalitis West Nile encephalitis *Most transmitted from reservoir to human by mosquitoes *Reservoirs are wild birds, small mammals *Cost ~$150 million per year, including vector control and surveillance activities.

West Nile Virus

*Mosquito-borne arboviral disease *Etiologic agent is a Flavivirus. *Mosquitoes become infected when they feed on infected birds. *Health effects vary from no symptoms to very severe symptomatology.

Transmission of Malaria

*Mosquitoes that carry a unicellular parasite known as a plasmodium. *Transmission involves the complex life cycle of mosquitoes (the vector) and human hosts (with human liver and human blood stages).

Plague

*The bacterium Yersinia pestis is the infectious agent for plague, a condition that infects both animals and humans. *Transmitted by the bite of a flea harbored by rodents. *Historians believe that the plague epidemic during the Middle Ages (the "black death") was caused by fleas from infested rats. *Reservoir: small mammals *Vector: several flea species *Plague cycles naturally in its enzootic foci, circulating between small mammals and fleas without human involvement. *Quiescent periods may last for years *Enzootic plague spills over from its natural cycle into the peridomestic and commensal rodent populations (and their fleas) *Poor sanitation, overcrowding and high numbers of rodents enhance urban plague transmission.

Cost of Malaria

*The economic costs in Africa alone were estimated at $1.8 billion in 1995. *Lost productivity, lost earnings, and negative impacts upon travel and tourism *The direct costs include those for treatment and prevention of the disease (e.g., medicine, hospitalization, and pesticide use)

Plague Clinical Spectrum

*The pathognomic sign of plague is a very painful, usually swollen, and often hot-to-the touch lymph node, called a bubo *Fever, extreme exhaustion, and history of exposure to rodents, rodent fleas, wild rabbits, or sick or dead carnivores *Onset of bubonic plague is usually 2 to 6 days after a person is exposed. Initial manifestations include fever, headache, and general illness, followed by the development of painful, swollen regional lymph nodes. *The disease progresses rapidly and the bacteria can invade the bloodstream, producing severe illness, called plague septicemia. *Progressive and potentially fatal illness generally results unless specific antibiotic therapy is given. *Progression leads to blood infection and, finally, to lung infection. *Pneumonic plague can be transmitted to others through the expulsion of infective respiratory droplets by coughing. *Incubation period of pneumonic plague: 1 to 3 days *Overwhelming pneumonia with high fever, cough, bloody sputum, and chills. *Case fatality rate for plague pneumonia >50%

Human Babesiosis

*Tickborne piroplasmosis (protozoan) *Caused by multiple species of Babesia *Transmitted by ticks Babesia microti (most common in U.S.) Babesia duncani Babesia divergens (Europe) *Ecology and epidemiology understudied Animal reservoir hosts? Tick vector spp.? True incidence/prevalence? Rate of coinfection with other TBD?

Control of Malaria - DDT

*Treating infected humans (reservoirs) *During mid-20th century, malaria was all but eliminated in many countries due to the use of pesticides, particularly DDT. *Thought to be harmful to wildlife, outdoor spraying of DDT was discontinued in many developed countries. *Some countries now permit the spraying of DDT inside of homes.

Bartonellosis

*Trench fever (B. quintana) *Cat-scratch disease (B. henselae) *Other Bartonella species

Mosquito Control

*Use sentinel chickens for surveillance. *Drain standing water; empty containers. *Introduce mosquito-eating fish into ponds. Judicious use *Repair window screens. *Use mosquito nets (incl. insecticide treated) *Wear repellents and protective clothing. *Avoid outdoor exposure during dawn/dusk of pesticides

Transmission of Zoonoses (method)

*contact with the skin (anthrax, American trypanosomiasis) *A bite or scratch from an animal (rabies, bartonellosis) *Direct inhalation or ingestion (anthrax, toxoplasmosis, hantavirus, typhoid) *The bite of an arthropod vector (tularemia, malaria, typhus, rickettsiosis)

Reemerging diseases

-Incidence increasing in existing host as result of changes in epidemiology -TB in HIV patients -Increased dengue due to urbanization

Emerging diseases

-infectious -incidence increasing following 1st introduction into new host sp.

Abroviral (4 symptoms)

1. Acute CNS [central nervous system] illness 2. Acute benign fevers of short duration, with and without an exanthum [rash] 3. Hemorrhagic fevers 4. Polyarthritis and rash, with or without fever and of variable duration

What percentage of emerging infectious diseases are comprised by zoonoses?

75%

Arthropod-Borne Viral Diseases

Also known as arboviral diseases. A group of viral diseases that are most frequently acquired when blood-feeding arthropod vectors infect a human host. Vectors that transmit arboviruses include ticks, sand flies, biting midges, and mosquitoes. Mosquitoes are most important in U.S.

Control of Flea and Tickborne Diseases

Avoid brushy/grassy/woody habitats? Inspect and treat pets with control products Wear light colored clothing Human "tick checks" Prompt removal of attached ticks "SAVE THE TICKS" Discourage animals from property Use repellents and pesticides safely Lawns: various pesticides People: DEET repellent; permethrin pesticide (clothing only)

Cat Scratch Disease

Bartonellosis "henselae"

Dengue Fever

Caused by flaviviruses DENV 1, 2, 3, 4 Vectors: Aedes aegypti, albopictus Primarily tropical areas: Southeast Asia, tropical Africa, South America ~100 mil cases worldwide/yr. Case-fatality rates as high as 40 to 50% untreated.

Dengue Fever in U.S.

DF does occur in the U.S. Southern states at risk for transmission from imported cases Sometimes local transmission (e.g., FL Keys)

Breakbone fever

Dengue

Zoonoses Factors Associated

Ecological changes that result from agricultural practices (e.g., deforestation, conversion of grasslands, and irrigation) Other factors include changes in the human population and human behavior, (e.g., wars, migration, and urbanization).

Tick - Ehrlichiosis and Anaplasmosis (from ticks)

Ehrlichia and Anaplasma preferentially infect leukocytes *Transmitted by different species of ticks *Disease resembles RMSF, except no rash in ~70% *Fever, HA, myalgia, chills, other flu-like symptoms *Leukopenia from destruction of leukocytes *Low mortality (5% or less) *Immune-compromised cases Blood transfusions Lab testing (slides, antibody tests, PCR) Treatment Doxycycline is the first line treatment for adults and children of all ages and should be initiated immediately whenever ehrlichiosis or anaplasmosis is suspected.

Bartonellosis Signs/Symptoms

F, HA, fatigue, depression, cognitive problems Rashes Lymphadenopathy

Dengue Hemorrhagic Fever (DHF)

High fever, severe headache, severe pain behind the eyes, joint pain, muscle and bone pain, rash, and mild bleeding (e.g., nose or gums bleed, easy bruising). *Younger children and those with their first dengue infection have a milder illness than older children and adults. *Dengue hemorrhagic fever (DHF): *Fever that lasts from 2 to 7 days, with signs/symptoms of dengue fever *When fever declines, symptoms including persistent vomiting, severe abdominal pain, and difficulty breathing, may develop. 24- to 48-hour period when capillaries become excessively permeable ("leaky"), allowing the fluid component to escape from the blood vessels into the peritoneum (causing ascites) and pleural cavity (leading to pleural effusions). *May lead to failure of the circulatory system and shock, followed by death, if circulatory failure is not corrected. *Patients with DHF have low platelet count and hemorrhagic manifestations, tendency to bruise easily or other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding. *No specific treatment

Tickborne Piroplasosis

Human Babesiosis Babesia microti (most common in US)

What months of the year is one most likely to contact RMSF?

June peak month (summer months)

Bartonellosis (Arthropod Vectors)

Lice (Trench fever - B. quinatana) Fleas (Cat scratch dis.-B. henselae; other spp.) Sand flies ( Ticks? (B. henselae? B. vinsonii?

Vector-Borne Diseases

Malaria Yellow fever Dengue fever West Nile and other arthropod-borne viruses Plague Bartonellosis Lyme disease Rocky Mountain spotted fever Ehrlichiosis Babesiosis

Zoonoses Examples (other)

Monkeypox (orthopoxvirus) Tularemia (Francisella tularensis) Rabies Anthrax (Bacillus anthracus) Psittacosis

Name of U.S.

Mosquito-borne: small, local outbreaks "Airport" malaria Congenital Transfusion-transmitted (~1 case/2 yrs)

Malaria Infectious Agents

Plasmodium falciparum is the most deadly Plasmodium vivax Plasmodium ovale Plasmodium malariae Plasmodium knowlesi

Emerging Zoonoses

Refers to zoonotic diseases that are caused by either apparently new agents or by known agents that occur in locales or species that previously did not appear to be affected by these known agents.

Control of Rodent Form Diseases

Remove harborage Wood or trash piles Inspect storage buildings Eliminate entry points Trapping Bait poisons

Human Babesiosis

Signs / Symptoms: Signs/symptoms: Asymptomatic F, chills, sweats, HA, fatigue Hemolytic anemia, jaundice, dark urine Low blood pressure Low platelets (thrombocytopenia) Disseminated intravascular coagulation (DIC) *Life threatening for immunocompromised Kidney, liver, lung, heart failure

Protection from Mosquitos

Spraying pesticide to kill mosquito larvae is as common as doing the daily laundry in Kolkata (Calcutta), India. In the ongoing battle against malaria outbreaks, inspectors check that people without faucets store water in closed containers, but monsoon rains that flood some sections of the city are harder to control. Standing water creates the perfect environment for mosquito larvae to breed.

Hantavirus Pulmonary Syndrome (HPS)

Symptoms Early, common: fatigue, fever, myalgia ~50% have HA, chills, abdominal symptoms Late: cough, shortness of breath, fluid in lungs 38% case-fatality rate

Quinine (Bark of Cinchona tree)

The first widely known remedy—from the bark of the cinchona tree—was discovered in the region in the early 1600s. The medicine, which became known as quinine, was so promising that malaria-ravaged Europe mounted expeditions to acquire the plant. Today, scientists search for more ways to fight the disease—including the development of a vaccine—as the parasite becomes resistant to the most common course of drugs.

Hantavirus (Deer mouse)

The main host for the hantavirus is the deer mouse--Peromyscus maniculatus, which is found throughout North America.

Bartonellosis Treatment

Various antibiotics Levofloxacin, ciprofloxacin, doxycycline, azithromycin, rifampin

Protection from Mosquitos

Veiled in old bed nets, dormitory residents at the Kafue Boys Secondary School in Kafue, Zambia, get a small measure of protection each night. But the mosquito barriers are only as good as the fabric from which they're made. Holes in the nets, untreated material, or an exposed hand or foot during sleep increase the odds that the malaria-carrying insects will bite.

Bartonellosis Risk Factors

Veterinary occupations Animal rescue Pets Other exposure to fleas, ticks

Xenopsylla cheopis (flea rat)

Xenopsylla cheopis (oriental rat flea) engorged with blood. This flea is the primary vector of plague in most large plague epidemics in Asia, Africa, and South America. Both male and female fleas can transmit the infection

Malaria highest risk in children

Younger children are at higher risk of dying; their bodies have not developed enough immunity to fight the disease, which can infect their brains and kill them. Each day malaria claims the lives of about 3,000 children in Africa—one every 30 seconds. Researchers predict that in 2007, malaria will strike up to a half billion people worldwide. About a million—most under five years old and living in Africa—will die.

Abroviral Diseases

a/k/a Arthropod-Borne Viral Diseases

Zoonosis Defined

an infectious disease whose agent normally lives in animals

Name the protozoan tickborne infection that is a major concern in terms of safety of blood supply?

babesiosis

Name one emerging vial zoonotic disease

hantaviruses

Yersinia pestis

infectious agent for plague that affects both animals and humans (see plague)

What disease especially common in Africa is transmitted by Anopheles spp. mosquitoes and is caused by several species of Plasmodium?

malaria

Zoonosis

refers to "an infection or infectious disease transmissible under natural conditions from vertebrate animals to humans." ~58% of known human pathogens ~75% of emerging disease ~71% EID with wildlife origin "Spillover" -When pathogen passes from one species as host into another—distinct event "Emergence" -Process/trend of pathogen becoming established in new host

Plasmodium falciparum (most virulent type of Malaria)

the most virulent of the four malaria parasites that infect humans—destroying red blood cells in the liver. It digests a cell's hemoglobin, multiplies inside to the point of rupturing the cell, and rapidly spreads a new generation of infection.