CS2 - Dengue Part 1 Flashcards
What are the criteria for Dengue ± warning signs?
Recent travel to or residence in an endemic area.
Fever with at least 2 of the following: rash, nausea, aches, positive tourniquet test, leukopenia, or any warning sign.
Laboratory-confirmed dengue virus infection.
What constitutes the criteria for Severe Dengue?
Severe plasma leakage leading to dengue shock syndrome and fluid accumulation with respiratory distress.
Severe bleeding.
Severe organ involvement, including liver (AST or ALT ≥1000 U/mL), CNS (impaired consciousness), heart, and other organs.
What does the tourniquet test highlight in dengue?
It highlights capillary fragility.
How is the tourniquet test performed?
Inflate a blood pressure cuff to a pressure between systolic and diastolic pressure.
Leave the cuff inflated for 5 minutes.
After 2 minutes, count the number of petechiae (small red or purple spots).
If there are ≥10 petechiae per 1 inch², the test is considered positive.
What are the basic components of a non-enveloped virus?
Capsid: Protein coat that protects the viral genome.
Nucleic acid: The viral genome, which can be either RNA or DNA.
What are the basic components of an enveloped virus?
Capsid: Protein coat that protects the viral genome.
Nucleic acid: The viral genome, which can be either RNA or DNA.
Glycoprotein: Proteins on the viral surface that interact with host cell receptors.
Lipid bilayer: Membrane derived from the host cell that surrounds the viral capsid.
What family does the Dengue virus belong to?
Flaviviridae family.
What type of genome does the Dengue virus have?
+ssRNA (~11kb).
What are the structural proteins of the Dengue virus?
Capsid (C)
Membrane (M)
Envelope (E)
What are the non-structural proteins of the Dengue virus?
NS1
NS2A-B
NS3
NS4A-B
NS5
What is the first step of Dengue virus replication?
E-protein binds to host receptors (macrophages and dendritic cells).
What happens during steps 2-4 of Dengue virus replication?
Receptor-mediated endocytosis and early endosome packaging.
What occurs during steps 5-6 of Dengue virus replication?
Acidification, membrane fusion, and capsid release
What happens in step 7 of Dengue virus replication?
Viral RNA is released.
What occurs in step 8 of Dengue virus replication?
Translation and formation of the replication complex.
What happens in step 9 of Dengue virus replication?
Replicated genome and viral protein assembly.
What occurs in steps 10-11 of Dengue virus replication?
Maturation and release.
What is the typical incubation period for Dengue virus?
The incubation period is typically 8-12 days.
What factors influence the incubation period of Dengue virus?
The incubation period can vary based on the strain of the virus and the immune response of the individual.
Is non-mosquito transmission of Dengue virus possible?
Yes, non-vector transmission can occur, although it is rare
What are some possible forms of non-vector transmission for Dengue virus?
Non-vector transmission may include:
Vertical transmission from mother to child during pregnancy or at birth.
Blood transfusions or organ transplants.
Needle-sharing among intravenous drug users.
Can Dengue virus be transmitted through sexual contact?
There is no strong evidence to support sexual transmission, though some cases have been reported.
Does Dengue virus transmit through casual contact or aerosolized droplets?
No, Dengue virus does not transmit through casual contact or aerosolized droplets. It is primarily transmitted through mosquito bites.
What are some common diagnostic tests for Dengue?
Common diagnostic tests for Dengue include:
Viral isolation
RNA detection
NS1 antigen detection
IgM and IgG detection
What is a key challenge in interpreting IgM and IgG tests for Dengue?
Cross-reactivity due to infection or vaccination against other flaviviruses can lead to false positives when detecting IgM and IgG for Dengue.
What factor affects the specificity and accessibility of Dengue diagnostic tests?
The availability and accuracy of tests such as RNA detection, NS1 antigen, and serological tests can vary depending on specificity and accessibility of the healthcare settings.
What are the three main methods of vector control for Dengue?
The three main methods of vector control are:
Environmental
Biological
Chemical
What is involved in environmental vector control for Dengue?
Environmental control involves reducing mosquito breeding sites by:
Eliminating standing water
Proper waste management
Improving sanitation and water storage practices.
What is biological control in the context of vector control for Dengue?
Biological control includes using natural predators, such as fish that eat mosquito larvae, or introducing bacteria like Wolbachia to reduce mosquito populations.
What is chemical control in vector control for Dengue?
Chemical control involves using insecticides, such as pyrethroids, to kill mosquitoes and prevent the spread of Dengue.
What are some environmental approaches to control mosquito breeding sites in trees?
Environmental approaches to control mosquito breeding sites in trees include:
Filling holes in trees
Using skimmers
Regular cleaning.
What can be done to prevent mosquitoes from breeding in water containers?
o prevent mosquito breeding in water containers, one should:
Overturn or cover containers when not in use
Remove containers before rain.
How can larvicides or predators help in controlling mosquito populations?
Larvicides and natural predators, such as fish that consume mosquito larvae, can help reduce mosquito populations in stagnant water sources.
What other general cleaning practices can help reduce mosquito breeding?
General cleaning practices include:
Repairing broken containers
Keeping areas clear of standing water
Regularly cleaning containers, tanks, and gutters to prevent water accumulation.
What are biological approaches for controlling mosquito populations?
Biological approaches to controlling mosquito populations include:
Introducing natural predators such as fish that eat mosquito larvae.
Using microbial agents like Bacillus thuringiensis israelensis (BTI) that produce toxins toxic to mosquito larvae.
Releasing genetically modified mosquitoes that either do not transmit the virus or have reduced lifespan to control population numbers.
How does Bacillus thuringiensis israelensis (BTI) work as a biological control for mosquitoes?
Bacillus thuringiensis israelensis (BTI) is a bacterium that produces toxins specifically lethal to mosquito larvae. When applied to water bodies, it kills the larvae without harming other organisms.
What role do genetically modified mosquitoes play in vector control?
enetically modified mosquitoes can be engineered to either:
Have reduced lifespan, leading to a decrease in mosquito populations.
Carry genes that prevent them from being able to transmit the dengue virus to humans.
What is the Release of Insects with Dominant Lethal Gene (RIDL) approach in vector control?
RIDL involves genetically modifying insects to carry a dominant lethal gene that causes the insect to die before reaching adulthood or breeding age. This reduces the population of disease-carrying mosquitoes over time.
How does the RIDL approach work in controlling mosquito populations?
In RIDL, mosquitoes are engineered to express a lethal gene (e.g., tTAV) that causes death when the insect is exposed to a particular substance, such as tetracycline. In the absence of tetracycline, the gene leads to the mosquito’s premature death
What role does the tTAV protein play in RIDL technology?
he tTAV protein in RIDL is a transcriptional activator that controls the expression of a dominant lethal gene. When tetracycline is present, the tTAV protein is suppressed, preventing the lethal gene from being activated and allowing the mosquitoes to survive.
What is the function of the DsRed marker in RIDL mosquitoes?
The DsRed marker is used as a visual indicator to distinguish genetically modified mosquitoes from wild-type mosquitoes. It fluoresces red under certain lighting, making it easy to track and monitor the release of these modified mosquitoes.
What is Oxitec’s role in the Release of Insects with Dominant Lethal Gene (RIDL) approach?
Oxitec is a biotechnology company that developed the RIDL technology. They genetically modify mosquitoes to carry a dominant lethal gene that causes the mosquito to die before reaching adulthood or breeding age, ultimately reducing mosquito populations that spread diseases like dengue, Zika, and malaria.
How does Oxitec’s RIDL technology work in mosquito control?
Oxitec modifies mosquitoes with a gene that causes them to die under certain conditions (e.g., in the absence of tetracycline). These mosquitoes are released into the environment, where they mate with wild mosquitoes, passing the lethal gene to offspring, leading to a reduction in the overall mosquito population over time.
What is the significance of the dominant lethal gene in Oxitec’s RIDL mosquitoes?
The dominant lethal gene in Oxitec’s RIDL mosquitoes ensures that the insects die before they can reproduce. This gene is activated only under specific conditions, such as the absence of tetracycline, which is used to control the activation of the lethal gene.
What is the role of Wolbachia in mosquito control?
Wolbachia is a genus of bacteria that naturally infects many insect species, including mosquitoes. The bacteria can be used in mosquito control by manipulating mosquito reproduction. When infected with Wolbachia, mosquitoes are unable to reproduce with non-infected mosquitoes, leading to population decline.
How does Wolbachia affect mosquito reproduction?
Wolbachia causes cytoplasmic incompatibility (CI) in mosquitoes. Infected males can only successfully mate with infected females, and the eggs laid by uninfected females, when fertilized by infected males, will not hatch. This leads to reduced mosquito populations over time as the incompatibility prevents successful reproduction.
What are the advantages of using Wolbachia for mosquito control?
Using Wolbachia to control mosquitoes is environmentally friendly, as it doesn’t rely on chemical insecticides. It also reduces the spread of mosquito-borne diseases like dengue, Zika, and chikungunya by significantly decreasing mosquito populations or altering their reproductive capabilities.
How is Wolbachia introduced into mosquito populations?
Wolbachia is introduced into mosquito populations through mass release programs. Infected mosquitoes are bred in laboratories and released into the wild, where they mate with wild mosquitoes, spreading the bacteria. Over time, this leads to a widespread reduction in mosquito populations due to reproductive incompatibility.
What challenges are associated with using Wolbachia for mosquito control?
Challenges include ensuring the long-term persistence of Wolbachia in wild mosquito populations, managing potential ecological impacts, and overcoming public resistance to the release of genetically modified or infected mosquitoes. Also, regulatory hurdles may arise as Wolbachia programs expand.
What are larvivorous copepods used for in mosquito control?
Larvivorous copepods are small aquatic organisms that feed on mosquito larvae. By introducing these copepods into water bodies where mosquitoes breed, they help reduce mosquito populations by consuming the larvae before they can mature into adult mosquitoes.
What is the role of Gambusia affinis in mosquito control?
Gambusia affinis, commonly known as mosquito fish, are predatory fish that feed on mosquito larvae. These fish are introduced into water bodies where mosquitoes breed to naturally control the larval population and reduce the number of adult mosquitoes.
Q
How does the entomopathogenic fungus help control mosquito populations?
Entomopathogenic fungi, such as Beauveria bassiana, infect and kill mosquitoes by penetrating their exoskeletons and releasing toxins. These fungi are used in biological control programs to reduce mosquito populations by infecting mosquitoes in both larval and adult stages.
What is the role of Bacillus thuringiensis in mosquito control?
Bacillus thuringiensis is a bacterium that produces toxins toxic to mosquito larvae. The bacterium is applied to water sources where mosquitoes breed, killing the larvae when ingested. It is widely used as a biological larvicide, safe for humans, animals, and other non-target species.
What are the advantages of using biological approaches, such as larvivorous copepods or Bacillus thuringiensis, for mosquito control?
Biological approaches are eco-friendly and target only mosquitoes, reducing the risk to other species. They help reduce reliance on chemical insecticides, which can have negative environmental impacts, and provide a sustainable solution for long-term mosquito control.
What are the main characteristics of organochlorines as mosquito control agents?
Organochlorines are lipid-soluble insecticides that are environmentally damaging. They include the DDT class, which prolongs Na+ channel opening in mosquitoes, disrupting nerve function. However, their environmental persistence has led to concerns about ecological harm.
How do organophosphates work as insecticides?
Organophosphates are highly toxic insecticides that irreversibly inhibit acetylcholinesterase (AchE), an enzyme critical for nerve function. This inhibition causes an accumulation of acetylcholine, leading to overstimulation of the nervous system and eventually the death of the mosquito. Organophosphates are harmful to mammals as well.
What is the mechanism of action of carbamates as insecticides?
Carbamates are derived from carbamic acid and reversibly inhibit acetylcholinesterase (AchE). This inhibition leads to the accumulation of acetylcholine in the nervous system, resulting in paralysis and death of the mosquito. Carbamates are less toxic to mammals than organophosphates.
How do pyrethroids work as mosquito insecticides?
Pyrethroids are synthetic insecticides modeled after natural pyrethrins. They work by prolonging Na+ channel opening in mosquitoes, leading to nerve overstimulation and paralysis. Pyrethroids are effective at controlling mosquito populations but can cause resistance over time.
What are the environmental concerns related to organochlorines?
Organochlorines are highly persistent in the environment, which can lead to long-term ecological damage. They can accumulate in the food chain and affect non-target organisms, including wildlife and beneficial insects, and may lead to environmental contamination that persists for years.
What is the key difference between organophosphates and carbamates in terms of their effects on acetylcholinesterase?
Organophosphates irreversibly inhibit acetylcholinesterase (AchE), leading to permanent enzyme inhibition, while carbamates only reversibly inhibit AchE, meaning the enzyme can regain function over time after the insecticide’s effect dissipates.
What is penetration resistance in the context of insecticide resistance?
Penetration resistance occurs when the mosquito’s outer cuticle becomes more impermeable, preventing the insecticide from entering the body. This resistance mechanism reduces the effectiveness of the insecticide by limiting its ability to reach internal target sites.
How does metabolic resistance work in mosquitoes?
Metabolic resistance occurs when mosquitoes increase the production of enzymes that break down or detoxify insecticides before they can exert their toxic effects. Common enzymes involved in metabolic resistance include cytochrome P450s, esterases, and glutathione S-transferases.
What is target site modification or downregulation in insecticide resistance?
Target site modification or downregulation involves changes to the molecular target of the insecticide, such as Na+ channels, acetylcholinesterase, or other critical proteins. These changes either reduce the insecticide’s binding affinity or decrease its activity, making the insecticide less effective.
What is behavioral resistance in mosquitoes?
Behavioral resistance refers to changes in the mosquito’s behavior that reduce exposure to insecticides. This can include avoiding treated areas, altering feeding patterns, or changing resting sites to evade contact with insecticide-treated surfaces or areas.
How does penetration resistance impact the effectiveness of chemical insecticides?
Penetration resistance limits the amount of insecticide that can enter the mosquito, reducing its lethal effect. This resistance can make chemical control methods less effective, especially when using surface applications of insecticides.
What role do metabolic enzymes play in metabolic resistance?
Metabolic enzymes play a key role in metabolic resistance by breaking down or neutralizing insecticides before they can cause harm. For example, cytochrome P450 enzymes can metabolize pyrethroids, and esterases can break down organophosphates, rendering these insecticides ineffective.
What is the impact of target site modification on the development of resistance?
Target site modification leads to a reduction in the insecticide’s ability to bind to or affect its target, making the insect resistant to the chemical. This can occur through mutations in the target protein, such as changes in Na+ channels that reduce the insecticide’s binding and effectiveness.
How does behavioral resistance reduce the effectiveness of insecticides?
Behavioral resistance reduces insecticide effectiveness by altering the mosquito’s behavior, such as avoiding treated areas or not feeding on treated surfaces. This reduces the exposure to insecticides, preventing them from having the desired lethal effect on the mosquito population.
How can dengue and chikungunya be distinguished?
Dengue and chikungunya can be distinguished by symptoms and diagnostic tests. Dengue may progress to severe dengue with dengue shock syndrome and can involve bleeding. Chikungunya typically presents with high fever, severe joint pain, and rash, but does not usually cause severe shock or bleeding.
What is the risk of dengue infection progressing?
Dengue can progress to severe dengue, which can include dengue shock syndrome (DSS), severe bleeding, and organ failure. Severe dengue is a life-threatening condition that requires prompt medical attention.
How many viral serotypes cause dengue?
Dengue virus consists of 4 serotypes, each causing infection. Infection with one serotype typically provides lifelong immunity to that serotype but only partial immunity to the others.
What mosquitoes are primarily responsible for spreading dengue?
Dengue is predominantly spread by female Aedes aegypti and Aedes albopictus mosquitoes, which are active during daylight hours.
Why is the burden of dengue increasing globally?
The burden of dengue is increasing due to the invasiveness of Aedes aegypti and Aedes albopictus mosquitoes, which have expanded into new regions and environments.
How can the burden of dengue be minimized?
The burden of dengue can be minimized through effective vector control mechanisms, such as eliminating mosquito breeding sites, using insecticides, and implementing biological control strategies.
What is the global burden of Dengue fever?
Dengue fever has become a major global health concern, with an increasing burden, especially in tropical and subtropical regions. It’s one of the most prevalent mosquito-borne viral diseases worldwide, causing millions of infections annually. The disease burden has risen due to the expansion of Aedes aegypti and Aedes albopictus mosquito populations into new regions
How does the dengue virus replicate?
The dengue virus is an RNA virus that replicates inside the host’s macrophages and dendritic cells. The virus enters host cells through receptor-mediated endocytosis, followed by the release of viral RNA into the cytoplasm. Translation and replication occur in the cytoplasm, followed by assembly of new viral particles, which are then released to infect other cells.
What are the modes of transmission of dengue?
Dengue is primarily transmitted by the bite of infected female Aedes mosquitoes (Aedes aegypti and Aedes albopictus). The mosquitoes become infected when they bite a person already infected with the virus. The virus can also be transmitted vertically from infected mother to offspring and potentially through blood transfusions.
What are the symptoms of dengue fever?
Common symptoms of dengue fever include high fever, severe headache, retro-orbital pain, muscle and joint pain, rash, and leukopenia. The fever lasts for 2-7 days and is often followed by a period of recovery. Some individuals may develop a rash or positive tourniquet test showing signs of capillary leakage.
What are the symptoms of severe dengue?
Severe dengue includes more serious symptoms such as severe plasma leakage, leading to dengue shock syndrome (DSS), severe bleeding, and organ failure. Dengue hemorrhagic fever (DHF) can cause bleeding, thrombocytopenia, and damage to organs like the liver (AST or ALT ≥1000 U/mL), CNS impairment, and cardiac complications.
What are the diagnostic methods for dengue fever?
Viral Isolation:
Advantage: Gold standard for confirmation.
Disadvantage: Time-consuming and labor-intensive.
RNA Detection (RT-PCR):
Advantage: Highly sensitive and specific for early infection.
Disadvantage: Requires specialized equipment and training.
NS1 Antigen Detection:
Advantage: Detects early viral presence, especially in the first few days.
Disadvantage: Cross-reactivity with other flaviviruses can lead to false positives.
IgM and IgG Antibody Detection:
Advantage: Useful for later stages of infection and serological surveys.
Disadvantage: Cross-reactivity with other flaviviruses (e.g., Zika, yellow fever).
Vector Control Methods
Q: What are the vector control methods for dengue?
Various vector control methods are employed to reduce the mosquito population and minimize dengue transmission:
Environmental Approaches:
Removing or covering stagnant water sources to reduce breeding sites.
Regular cleaning and maintenance of containers, gutters, and other water-holding objects.
Use of mosquito meshes and physical barriers.
Biological Approaches:
Release of Wolbachia-infected mosquitoes: These mosquitoes reduce the lifespan and reproductive capacity of Aedes mosquitoes, preventing dengue transmission.
Release of genetically modified mosquitoes (e.g., RIDL): Introduces mosquitoes with dominant lethal genes, leading to population collapse.
Larvivorous fish and copepods that consume mosquito larvae.
Chemical Approaches:
Insecticides like pyrethroids, organophosphates, and carbamates to kill adult mosquitoes and larvae.
Larvicides to target mosquito larvae in breeding sites.
Advanced Biological Methods:
Wolbachia Bacteria: Introduced into mosquitoes to sterilize them, decreasing population levels by preventing reproduction.
Genetically Modified (GM) Mosquitoes: Release of mosquitoes with altered genetic material to reduce population size or spread a trait that prevents the virus from replicating.
: Why are biological methods of vector control considered advanced?
Biological methods of vector control, such as Wolbachia infection or genetically modified mosquitoes, target the mosquito population’s reproductive cycle, creating more sustainable, long-term solutions compared to chemical methods. They also minimize environmental impact and resistance development in mosquitoes.
