Vector Transmitted Diseases 2023 PDF

41 –Vector Transmitted Diseases BioMi 2900 Learning objectives To understand the life cycle and transmission of rabies virus and how it remains an important zoonotic disease today Dengue fever virus mode of transmission and possible vaccine development Life cycle of Malaria L...

41 –Vector Transmitted Diseases BioMi 2900 Learning objectives To understand the life cycle and transmission of rabies virus and how it remains an important zoonotic disease today Dengue fever virus mode of transmission and possible vaccine development Life cycle of Malaria Life cycle of Lyme Disease, transmission and how we can stop the spread!  Vector-borne diseases Transmitted to a human by the bite of an arthropod ‘vector’ (insect, tick), infects but doesn’t cause serious disease in the vector NOTE: About Rabies (-)ssRNA genome Usually transmitted to a person by bite (saliva) from an infected animal. It is not considered vector borne but rather a zoonotic disease (from animal to human). The virus replicates well in nervous tissue and travels within nerves to the brain, then excreted in the saliva Wash the wound, post-exposure prophylaxis may be necessary If your pet is Rabies infection in suspected of humans is very slow associating (9+ months), thus with a rapid passive immunization wild animal, is required (injection quarantine of human antibodies) for 10 days and watch for symptoms Life cycle of rabies virus https://basicmedicalkey.com/rabies-2/ Diagnosis and Treatment for 60,000 deaths a year worldwide 1-2 deaths a year in the US Rabies Post-Mortem: Vaccinate your pets! Prophylacti Under the There is an efficacious cs: microscope, viral vaccine (inactivated virus) Injection of inclusions called Vets, animal workers are Human Negri bodies are routinely vaccinated antibodies found in the against cytoplasm rabies virus Diagnosis and Treatment for Rabies Post-Mortem: Vaccinate your pets! Prophylacti Under the There is an efficacious cs microscope, viral vaccine (inactivated virus) Injection of inclusions called Vets, animal workers are Human Negri bodies are routinely vaccinated antibodies found in the against cytoplasm rabies virus Source: WHO In the US, 20,000 people receive prophylactics/year If rabies is largely found in wild animal populations, will we ever defeat rabies? A. Yes, if we vaccinate every domestic animal B. Yes, if we leave oral rabies vaccine in food baits for wild animals to pick up and eat C. Yes, if we constantly sample wild animals for rabies D. No, we can’t! Rabies-free https://www.gov.uk/government/ areas of the publications/rabies-risks-by-country/ world Source: rabies-risks-in-terrestrial-animals-by- WHO country Dengue Fever Virus Emerging infectious disease Dengue (virus): Dengue is the most common arboviral disease (viral disease transmitted by an arthropod vector) ~390 million infections and 100 million new cases each year, a small proportion of these cases progress to severe dengue. Dengue Hemorrhagic Fever: bleeding, respiratory distress, dramatic drop in blood pressure Roughly 1 in 2,000 dengue cases result in death. There are 4 known serotypes for Dengue Example: 2018 To identify the Dengue virus serotypes and genotypes circulating in Chennai, Tamil Nadu, India. Source: Microbiology Section DOI : 10.7860/JCDR/2018/ 36313.12392 Antibody dependent enhancement and vaccines for Dengue There are 4 known serotypes for Dengue  Malaria (protist - Plasmodium): causes more than 600,000 deaths every year globally, most Malaria of them children under 5 years of age. sporozoites gamatocyt Lyme disease Agent: Borrelia burgdorferi Spirochete, Gram-negative but no LSP, up to 30 µm long corkscrew, motility enhances ability to be transmitted and maintain the bacterial infection Genome arrangement: one linear chromosome, at least 17 linear and circular plasmids. Plasmids easily lost during culturing in vitro. Transmission: to humans by Ixodes tick bite, humans appear to be an “accidental host” In the Northeast US, only the blacklegged tick transmits Borrelia, and it is believed that most cases arise from nymph bites  Complex life cycle of tick contributes to persistence In Northeast US, primary reservoirs for B. burgdorferi: white-footed field mice and other small warm-blooded animals To reproduce, the tick must have three blood meals -- it picks up Borrelia with the first meal on an infected rodent Deer do not become infected with Borrelia but are important in transport of the tick Lyme disease Symptoms: First phase (days to first few weeks after transmission), severe headache, fever, fatigue, common but not always a bull’s eye rash (as bacteria spread in the skin) Second phase (weeks to months), neurological issues – face paralysis (Bell’s palsy), arthritis, carditis (inflammation of the heart) Third phase (months to years), arthritis especially in knees, tiredness, continued neurological issues  Virulence factors: Outer surface proteins (OSP) – bind host cells Gene duplication and rearrangements of genes coding for OSPs lead to antigenic diversity in surface proteins Motility – transmission and movement within host tissues Treatment: Most Lyme disease cases can be effectively treated with antibiotics (doxycycline or amoxycillin) If treated early in infection cycle, oral antibiotics are effective, more advanced cases may require intravenous antibiotics (vaccine no longer available) https://www.aamc.org/news/lyme-disease-rise-why- there-still-no-vaccine  Lyme disease is considered an “emerging disease” and it is the most prevalent vector-borne human disease in the US. First described in 1977, increase in arthritis in children in Old Lyme, CT. But cases occur elsewhere in US, Europe and Asia. What measures would you recommend to control Lyme Disease? A. Eradicate suburban deer populations B. Use insecticides to kill ticks in the wild C. Kill all mice D. Develop a better vaccine E. Start a campaign to test people for Borrelia and treat those infected Borrelia burgdorferi pathogenesis is an immune system over-activation The immune system of natural host (rodents) has evolved to ignore Borrelia (no disease symptoms). Borrelia is a sprinter - ~ 4 µm/s in tissue! Outruns phagocytes. All secondary effects of Borrelia dissemination are caused by immune system activation (similar to autoimmune disorders  arthritis) Here is my first Your immune system Mem e ever? What Borrelia do you think ? One final thought about vector transmitted disease:  Gene Drives could help to reduce the burden of vector transmitted diseases https:// targetmalaria.org/what- we-do/how-it-works/ Gene Drive explained in a 2 minute video: https://wyss.harvard.edu/technology/gene Sources: the Scientist Magazine Can genetically engineered mice permanently curb Lyme disease? David Abel | Boston Globe | May 5, 2022