![Arthropod-Borne Viral
Diseases (Arboviral)
• A group of viral diseases that can be acquired when
blood-feeding arthropod vectors infect a human host.
• Vectors that transmit arboviruses include ticks, sand
flies, biting midges, and mosquitoes.
Four Main Clinical Symptoms of Arboviral Disease
1. Acute CNS [central nervous system] illness
2. Acute self-limited fevers, with and without exanthum [rash]
3. Hemorrhagic fevers
4. Polyarthritis and rash, with or without fever and of variable duration](https://image.slidesharecdn.com/chapter05-240130211426-a87cfc2a/85/HLTH-104-Chapter-05-26-320.jpg)
HLTH 104 Chapter 05
- 1. Chapter 5 Zoonotic and Vector-Borne Diseases
- 2. Learning Objectives By the end of this chapter the reader will be able to: • Provide a rationale for environmental change and infectious disease occurrence • Indicate how a disease may be transmitted from an animal reservoir to humans • Define the terms vector-borne and zoonotic diseases, giving examples • List three human diseases transmitted by arthropod vectors • Discuss methods used to control vector-borne and zoonotic disease
- 3. Zoonosis • Refers to “an infection or infectious disease transmissible under natural conditions from vertebrate animals to humans.” • Methods of transmission: o Contact with the skin o A bite or scratch from an animal o Direct inhalation or ingestion o The bite of an arthropod vector • See Table 5-2 for examples
- 4. Zoonosis
- 5. Bacterial Shapes Bacteria get part of their name from their shape and interaction with other bacteria.
- 6. Bacteria vs. Virus A virus is harder to deal with because it is much smaller and invades healthy cells to use as a host.
- 7. Vector • Defined as “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 o Various species of rodents (rats and mice) o Arthropods (mosquitoes, ticks, sand flies, biting midges)
- 8. Vector-Borne Diseases • Generally spread by blood feeding vectors (Biological transmission) • Increased through environmental factors • Examples (details in the following slides): o Malaria o Leishmaniasis o Plague o Lyme disease o Rocky Mountain spotted fever
- 9. Malaria • A disease found in more than 100 countries, with more than 50% 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 more than 1 million persons. • Global direct economic costs incurred by malaria are estimated to be $12 billion U.S. annually o The direct costs include those for treatment and prevention of the disease o Lost productivity, lost earnings, and negative impacts upon travel and tourism
- 10. Transmission • Principle vector for malaria is the Anopheles mosquito which carry a plasmodium (unicellular parasite) • Involves the complex life cycle of mosquitoes (the vector) and human hosts (with human liver and human blood stages). Figure 5-3 Female Anopheles gambiae mosquito feeding.
- 11. Symptoms • Fever and flu-like symptoms such as headaches, muscle aches, fatigue, and shaking chills o 9 to 14 days after bite of an infected mosquito o Life-cycle Figure 5-4 • Other symptoms to follow can be jaundice, kidney failure, seizures, mental confusion, coma, and ultimately death.
- 12. Figure 5-4 The life cycle of the parasites of the genus Plasmodium, causal agents of malaria.
- 13. Control of Malaria • During mid-20th century, efforts to control malaria by spraying with DDT and administering synthetic antimalaria drugs were found to be effective. • Thought to be harmful to wildlife; use of DDT was opposed by many developed nations, especially the U.S. • South Africa has (and to some extent still) used annual spraying of DDT inside of homes. • Other control methods are to use bed nets and control areas with standing water to reduce breeding grounds
- 14. Leishmaniasis • The reservoir for the cutaneous form of leishmaniasis includes wild rodents, human beings, and carnivores (e.g., domestic dogs). • Transmitted from the reservoir to the human host by a sand fly known as the phlebotomus fly.
- 15. Transmission • Caused by the transmission of a protozoal organism that exist in two forms o Promastigotes and amastigotes • Present in the countries around the Mediterranean and endemic in a total of 82 countries • The annual incidence is around 600,000 • The reason for increasing cases are: o Movement of the human population into endemic areas o Increasing urbanization o Extension of agricultural projects into endemic areas o Climate change due to global warming
- 16. Transmission
- 17. 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.
- 18. Figure 5-14 World distribution of reported plague cases by country, 2000-2009. Modified and reproduced from Centers for Disease Control and Prevention. Plague. Maps and statistics. Available at: https://www.cdc.gov/plague/maps/index.html. Accessed January 29, 2017. * Data reported to World Health Organization (WHO). ** Dot placed in center of reporting country.
- 19. Plague • Etiology • Once transmitted to humans, it can progress in stages o Bubonic plague – fever, chills, headache o Lymphandenitis – infected lymph nodes o Pneumonic plague – communicable through respiratory droplets • Untreated bubonic plague has a fatality rate from about 50 – 60% • Controlled by mainly public awareness and controlling the rodent population
- 20. 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 bacterial spirochete known as Borrelia burgdorferi (image below). • Transmission of Lyme disease to humans is associated with infected black-legged ticks (Ixodes scapularis) that ingest blood by puncturing the skin of the host • A total of 28,453 confirmed cases were reported to the CDC in 2015. Most in the Northeast (see map)
- 21. Figure 5-16 (Top) From left to right: The black-legged tick adult female, adult male, nymph, and larva. Source: Adapted and reprinted from the Centers for Disease Control and Prevention. Lyme Disease. Available at: http://www.cdc.gov/ncidod/dvbid/lyme/ld_transmission.htm. Accessed March 14, 2010.
- 22. Figure 5-17 Number of reported cases of Lyme Disease by county – United States 2007
- 23. Treatment and Prevention • Signs o Red, expanding rash called erythema migrans (EM) o Fatigue, chills, fever, headache, muscle and joint aches, and swollen lymph nodes • Antibiotic therapy exists for cases that are caught early • Preventative measures: o Take caution when clearing brush or landscaping o Be aware when you are in areas that ticks inhabit o Wear light colored clothing and inspect yourself after leaving an outdoor area
- 24. Rocky Mountain Spotted Fever • Causal agent is Rickettsia rickettsii, a rickettsial agent. o Transmitted by the bite of an infected American dog tick or Rocky Mountain wood tick • A febrile disease with sudden onset of high fevers that may last up to 3 weeks. • Case fatality rate can range up to 25% among untreated patients o Much lower when treated early with antibiotics
- 25. Viral Hemorrhagic Fevers (VHF) • Viruses that cause VHFs require an animal host or insect host (arthropod vector) as a natural reservoir. • Examples of animal host reservoirs include rodents such as the cotton rat, deer mouse, and house mouse. • The viruses are limited to those geographic areas in which the host species reside. Examples of VHFs discussed in this chapter are: o Hantavirus pulmonary syndrome (see emerging zoonoses) o Dengue hemorrhagic fever (covered in the section on emerging and reemerging infections)
- 26. Arthropod-Borne Viral Diseases (Arboviral) • A group of viral diseases that can be acquired when blood-feeding arthropod vectors infect a human host. • Vectors that transmit arboviruses include ticks, sand flies, biting midges, and mosquitoes. Four Main Clinical Symptoms of Arboviral Disease 1. Acute CNS [central nervous system] illness 2. Acute self-limited fevers, with and without exanthum [rash] 3. Hemorrhagic fevers 4. Polyarthritis and rash, with or without fever and of variable duration
- 27. Arboviral Encephalitides • Caused by a virus that produces an acute inflammation of: o Sections of the brain o Spinal cord o Meninges • Transmitted by the bite of an arthropod vector (primarily mosquitoes, midges, and sandflies) • The reservoir hosts for some forms of encephalitis viruses consist of nonhuman vertebrate hosts (e.g., wild birds and small animals). • Cost of arboviral encephalitides is approximately $150 million per year, including vector control and surveillance activities.
- 28. West Nile Virus • Classified as a mosquito-borne arboviral fever, the etiologic agent is a Flavivirus. • Mosquitoes are the carriers that become infected when they feed on infected birds. o See geographical map on page 113 for areas of reported cases • Health effects vary from no symptoms to very severe symptomatology. o Onset between 3 and 14 days o In severe cases, neurological effects can be permanent • See Fact Sheet on page 111
- 29. 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. • Factors in the rise of emerging zoonoses o Ecological changes that result from agricultural practices • Deforestation • Conversion of grasslands • Irrigation o Other factors include changes in the human population and human behavior (e.g., wars, migration, and urbanization)
- 30. Figure 5-21: Range and recognized site(s) of origin of a variety of emerging and re-emerging infections. v-CJD = variant Creutzfeldt-Jakob disease; E. coli = Escherichia coli.
- 32. Hantavirus Pulmonary Syndrome (HPS) • The causative agent is the hantavirus, part of the viral family known as Bunyaviridae. • May be transmitted when aerosolized (airborne) urine and droppings from infected rodents are inhaled. • Highly fatal condition transmitted mainly from four species of rodents: cotton rat, rice rat, white-footed mouse, and deer mouse. The main host for the hantavirus is the deer mouse--Peromyscus maniculatus, which is found throughout North America.
- 33. Dengue Fever • Caused by four flaviviruses that create illness that range from mild to severe o Dengue fever, Dengue Hemorrhagic Fever, and Dengue Shock Syndrome o The proportion of deaths can be as high as 40% to 50% when the disease is untreated. • Occurs primarily in tropical subtropical areas of the world, for example, Southeast Asia, tropical Africa, and South America. (figure 5-25) • The vector for transmission is the Aedes aegypti mosquito. o Resurged after the ban on DDT
- 34. FIGURE 5.25 World distribution of dengue—2008.
- 35. Dengue Fever in the U.S. • In the U.S., most cases of dengue are imported by travelers who are returning from endemic areas or by immigrants. o However, occurrence of dengue fever that originated in the continental U.S. has been documented. • Southern Texas and the southeastern states are at theoretical risk for transmission of dengue and for sporadic outbreaks. • The dramatic global resurgence is due to lack of effective mosquito control, population growth, and poor treatment of water and human waste.
- 36. Zika Virus • Zika is spread mostly by the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus). These mosquitoes bite during the day and night. o Research has also shown that the virus can be spread through sexual contact and blood transfusions (figure 5.27) • Most won’t have symptoms but some may develop a rash and a fever. • Greater risks are with pregnant mothers who can pass it along to a developing fetus which can cause microcephaly and other congenital defects. • Top 5 things you need to know about Zika o https://www.cdc.gov/zika/pdfs/Top5.pdf
- 37. Ebola Hemorrhagic Fever • Severe, often-fatal disease in humans and nonhuman primates (monkeys, gorillas, and chimpanzees) that has appeared sporadically since its initial recognition in 1976. • Incubation period for Ebola HF ranges from 2 to 21 days o Onset of illness is abrupt and is characterized by fever, headache, joint and muscle aches, sore throat, and weakness, followed by diarrhea, vomiting, and stomach pain. o A rash, red eyes, hiccups and internal and external bleeding may be seen in some patients. Ebola virus in the blood
- 38. Rift Valley Fever • An acute, fever-causing viral disease that affects domestic animals (such as cattle, buffalo, sheep, goats, and camels) and humans. • Humans can get RVF as a result of bites from mosquitoes or they are exposed to either the blood or other body fluids of infected animals • Patents have either no symptoms or a mild illness associated with fever and liver abnormalities. However, in some patients the illness can progress to hemorrhagic fever, encephalitis, or ocular disease.
- 39. Other Notable Zoonotic Diseases • Monkeypox o Rare o Contracted through a bite or direct contact with the infected animal’s blood, body fluids, or lesions • Tularemia o Potentially serious illness that occurs naturally in the United States. o It is caused by the bacterium Francisella tularensis found in animals (especially rodents, rabbits, and hares). o Also, can be contracted by consuming water or food that is contaminated with the bacterium
- 40. Other Notable Zoonotic Diseases Rabies • A highly fatal disease of the CNS caused by a virus that is transmitted through the bite of an affected animal. • Worldwide, dog bites are the principal source to humans. Rare now in the U.S. • In the U.S. after 1960 and the vaccination program, most case are now associated to wild animals (bats, raccoons, and skunk) Figure 5.33 • Early symptoms include irritability, headache, fever and sometimes itching or pain at the site of exposure. The disease eventually progresses to paralysis, spasms of the throat muscles, convulsions, delirium and death Treatment • vaccine is usually given in the upper arm for a total of 5 injections over a period of 28 days along with a one time dose of rabies immune globulin for immediate temporary immunity
- 41. Other Notable Zoonotic Diseases • Anthrax o Anthrax is a serious disease caused by Bacillus anthracis, a bacterium that forms spores o There are three types of anthrax: • skin (cutaneous), less fatal • lungs (inhalation), high fatality • digestive (gastrointestinal), rare o All three forms are treatable with antibiotics administered as soon as possible after exposure o Symptoms can be mild , and if ignored, become severe and death ensues
- 42. Other Notable Zoonotic Diseases • The three types of Influenza viruses are o Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. • The emergence of a new and very different influenza virus to infect people can cause an influenza pandemic. o Influenza A can infect a variety of animals, but certain strains can be specific to certain species o Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics.
- 43. Control of Mosquito-Borne Diseases • Use sentinel chickens and birds to monitor for presence of viruses. • Drain standing water. • Introduce mosquito-eating fish into ponds. • Wear repellents and protective clothing. • Repair window screens. FIGURE 5.35 Sentinel birds used to monitor for mosquito- borne viruses.
- 44. Check for Aedes mosquito breeding in your home
- 45. 1. Genetics 2. Our behavior 1. Lifestyle 2. Medical Care 3. Our environment Factors affect health and longevity We have control over 84% of disease vulnerability
- 46. Control Spread of Disease Understanding pathogen means of survival helps us learn how to control them Favorable O2 supply ◦ Aerobic versus anaerobic ◦ Facultative bacteria tolerate a range of O2 levels ◦ Manipulate O2 concentrations to destroy them Temperature requirements ◦ Thermophilic ,Mesophilic Psychrophilic ◦ Keep it hot, keep it cold, or don’t keep it long!
- 47. Control Spread of Disease Nutrition ◦ Keep utensils and surfaces clean (high heat) Moisture ◦ Need water to survive ◦ Keep dry food packages tightly sealed Unfavorable pH ◦ Prefer neutral, around 7.0 Change osmotic pressure ◦ Isotonic, Hypotonic, Hypertonic ◦ Reason why most foods have high sodium content to preserve its shelf life
- 48. Control Spread of Disease Absence of toxic materials ◦ As with most organisms, the introduction of a toxic substance prevents its growth or destroys its cell membrane Space ◦ Microbes divide rapidly in the proper environment ◦ Without proper space, toxins buildup and can kill off the colony
- 49. Defense against disease • First line of defense o Prevention; knowledge of disease • Second line of defense o Skin o Mucous membranes o Nutrition
- 50. Defense against disease • Third line of defense o Cellular defense (phagocytosis) o Active Immunity • Production of antibodies o Passive immunity • Required antibodies are introduced into the body • Natural or Artificial • Fourth line of defense o Curative medicine
Editor's Notes
- #10: (e.g., medicine, hospitalization, and pesticide use).