Test four Flashcards
Plasmodium
Disease organism
Family Culicidae
Mosquitoes
Great habitat diversity
Approximately 40 million years older than humans
Pests as well as vectors of pathogens causing human and animal disease
Subfamily
- Anophelinae - anopheles
2. Culicinae - aedes, culex, Haemagogus, Mansonia, Ochlerotatus and all other genera
Mosquito Characteristics
Bloodfeeding - only females take blood
Males and females feed on plant sugars
Larval biology - 4 stages (instars), aquatic, spiracle for breathing, filter-feeders, some cannibalistic, variable habitats
Malaria
Caused by a protozoan
Curable if promptly diagnosed and treated
Worse type of malaria
Plasmodium falciparum
Life cycle of Malaria
- A mosquito injects sporozoites into the blood stream
- They invade liver cells and transform into merozoites (this process is called exoerythrocytic schizogony. There are no disease symptoms during this stage
- Each cell ruptures, releasing tens of thousands of merozoites. Penetrating a red blood cell, a merozoite multiplies. This is called the erythrocytic stage (this is when clinical features develop)
- Each red cell bursts and releases more merozoites
- They infect more red blood cells and multiply again
- Some merozoites develop into male and female forms called qametocytes
- Feeding on a person with malaria a mosquito ingests the gametocytes
- They reproduce and develop into oocysts, which rupture and release sporozoites
- The sporozoites migrate from the mosquito’s gut to the salivary glands, ready to be injected into a human host
Erythrocytic Stage
intracellular parasite undergoes trophic phase
young trophozoite called ‘ring form’
ingests host hemoglobin
Exoerythrocytic Schizogony
hepatocyte invasion asexual replication 6-15 days 1000-10,000 merozoites no overt pathology
Sporogony
occurs in mosquito (9-21 d)
fusion of micro- and macrogametes
zygote ookinete (~24 hr)
ookinete transverses gut epithelium ('trans-invasion')
ookinete --> oocyst
asexual replication --> sporozoites
sporozoites released
sporozoites migrate through hemocoel
sporozoites 'invade' salivary glandsSymptoms of Encephalitis
Fever Headache Behavioral changes Altered level of consciousness Seizures
Encephalitis is
Acute inflammatory process affecting the brain
Encephalitis caused by
viruses or arboviruses
Arboviruses are
arthropod born viruses
Major arboviruses that cause encephalitis
Flaviviridae
Togaviridae
Bunyaviridae
Flaviviridae
West nile
st. louis encephalitis
Powassan virus
Togaviridae
E and W equine
Bunyaviridae
La Crosse
West Nile Virus
Primary host – wild birds
Principal arthropod vector – mosquitoes
1999 NY West Nile Outbreak
Crows dying in Queens, late summer
27 Deaths among captive birds
59 Human cases needing hospitalization, 7 deaths
Spread of West Nile in the US: 2000
spread throughout New England and Mid-Atlantic regions.
18 new human cases reported
Spread of West Nile in the US: 2001
spread throughout the entire eastern half of the US
64 cases reported, with NY, FL and NJ accounting for 60%
Spread of West Nile in the US: 2002
spread westward across Great Plains into Western US. Reached California by Labor Day.
By end of 2002 cumulative human cases > 3900, with > 250 deaths
Spread of the West Nile in the US: 2003
US, Canada, Mexico
9,858 cases reported to CDC, including 262 deaths in 45 states and D.C.
According to the CDC: What % of WN cases are fatal? sever forms kill?
Less than 1%
3-15%
St. Louis Encephalitis
Most common mosquito-transmitted human pathogen in the US
First isolated in 1933 in St. Louis, MO
St. Louis Encephalitis Case fatality ratio
5-15%
Easter Equine Encephalitis
Caused by a virus transmitted to humans and horses by the bite of an infected mosquito.
Average of 4 cases per year
Human cases occur relatively infrequently, largely because the primary transmission cycle takes place in swamp areas where populations tend to be limited.
E. Equine: 1831
First recognized as a disease in horses.
E. Equine: 1947
largest recorded outbreak in Louisiana and Texas. 13,344 cases and 11,722 horse deaths
W. Equine
Mosquito-borne
639 confirmed cases in the US since 1964
Important cause of encephalitis in horses and humans in North America, mainly in the Western parts of the US and Canada
W. Equine: 1912
25,000 horses died in Central Plains of US
La Crosse
On average 75 cases per year reported to the CDC
Most cases occur in children under 16 years old
Zoonotic pathogen that cycles between the daytime biting treehole mosquito, and vertebrate amplifier hosts (chipmunk, tree squirrel) in deciduous forest habitats
CDC’s “Three Ways to Reduce your West Nile Virus Risk”
Avoid mosquito bites
Mosquito-proof your home
Help your community
Yellow Fever
Caused by yellow fever virus (Flavivirus)
Transmitted predominantly by Aedes mosquitoes
Yellow Fever: Genus/Family
Flavivirus fibricus, Group B Arbovirus
Toga virus
YF Virus size? Consists of?
35-40 nm, single strand of RNA virus
Natural host of YF in Forest areas:
Primates non human
Vectors of YF in Forest areas:Africa
Aeded africanus
Vectors of YF in forest areas: S. America
Haemagogus
Vectors of YF in urban areas: African/S. America
Aedes aegypti
Rold of humans in YF Transmission
Incubation period of 2-6 days
Human become viremic; capable of infecting mosquitoes
The extrinsic incubation period in Ae. aegypti is 9–12 days
Clinical features of yellow fever: acute phase lasting? symptoms?
4-5 days a sudden onset of fever headache or backache muscle pain nausea Vomiting red eyes
YF can be strongly suspected when what is present?
Faget’s sign
Faget’s sign:
The simultaneous occurrence of a high fever with a slowed heart rate.
YF Toxic Phase presents with:
jaundice Bleeding from the gums, nose or in the stool vomiting blood diarrhea slow pulse in relation to fever
Dengue Fever spread by
mosquito
Dengue Fever: AKA, define
Breakbone fever
is an acute communicable disease caused by virus.
Dengue Fever: Infectious Agen
Dengue viruses (another RNA virus in the Flavivirus family)
DF highest in what area
Tropical and subtropical regions
More sever form of Dengue is:
Dengue Hemorrhagic fever
Symptoms of Dengue Hemorrhagic Fever
Severe and continuous pain in abdomen
Bleeding from the nose, mouth and gums or skin bruising
frequent vomiting with or without blood
stools, like coal tar
After several days the patient becomes irritable, restless, and sweaty
Three main forms of leishmaniasis
Cutaneous
Visceral
Mucocutaneous
Cutaneous
involving the skin at the site of a sandfly bite
Visceral
involving liver, spleen, and bone marrow
Mucocutaneous
involving mucous membranes of the mouth and nose after spread from a nearby cutaneous lesion (very rare)
Leishmania donovani
VISCERAL LEISHMANIASIS: involving endothelial tissue liver, spleen, and bone marrow.
Leishmania tropica (CL)
OLD WORLD CUTANEOUS LEISHMANIASIS: involving epithelial cells the skin at the site of a sand fly bite.
Leishmania brazilliensis (MCL)
NEW WORLD MUCOCUTANEOUS LEISHMANIASIS: involving mucous membranes of the mouth and nose after spread from a nearby cutaneous lesion.
Transmission of Leishmaniasis
By sand flies.
Artificial transmission of leishmania via the sharing of contaminated syringes and needles, from one intravenous drug user to another.
Rarely, Leishmaniasis is spread from a pregnant woman to her baby.
Blood transfusion is another possible mechanism of transmission.
Cutaneous Leishmaniasis: forms?
Cutaneous forms of the disease normally produce skin ulcers on the exposed parts of the body such as the face, arms and legs. The disease can produce a large number of lesions
Rocky mountain spotted fever
The most virulent of the “spotted fever group” of rickettsiae
First described in Idaho in the late 19th Century
Causative agent named Rickettsia rickettsii
The tick is the vector and main reservoir
Which tick is main vector of RMSF?
Dermacentor variabilis – American dog tick
RMSF: Causative agent?
Rickettsia rickettsii
RMSF: Clinical Manifestations
Incubation period of 2 to 14 days
Starts with fever, myalgia, headache (usually severe)
High temp- >1020 F in most
Nausea, vomiting, abdominal pain, diarrhea
Basic categories/examples of cultural techniques
Cropping tactics
Harvest Tactics
Sanitation
Benefits of cultural controls
Often easily incorporated into the production system
predictable level of control, even if partial
Fast acting
As a group, relatively sustainable
Disadvantages of Cultural Controls
Some are not environmentally benign (e.g. conventional tillage, residue burning)
May alter crop value or gross income (planting date, harvesting, spacing)
Some are labor/energy intensive (pruning, tillage)
Widespread adoption may be low
Many conflicts
Field Preparation & Planting
Plant & row spacing
Planting date (early vs late)
Planting method (depth, insertion method)
Mulches – organic & synthetic
Cropping Tactics
Trap/Barrier Crops
Intercropping
Cultivar mixtures
Trap/Barrier Crops
Trap crops are destroyed with the pest
planting plants that attract pests and then harvest or spray trap crop
Planting geraniums attracts Japanese beetles, which are poisoned by the geraniums
Barrier crops are on field perimeter
Intercropping
Two or more useful crops
Cultivar mixtures
Different cultivars may have to be planted in different fields to create a “cultivar patchwork”.
Water Management
flooding may destroy soil pests
light sprinkling at specific times may decrease ovipositioning of pests
Crop Rotation
Intercropping in time
Especially effective against soil-based pests: Weeds, soil-borne pathogens, root-feeding insects
For weeds:
Changes weed complex
Not stand alone weed mgmt, instead used to facilitate weed mgmt
Harvest Tactics
Harvest timing (early vs late) – may use early/late varieties.
Crop matures before pests build up
Harvesting operation itself causes extensive mortality.
Harvest method
Partial Harvesting – Prevents movement to high value crops
Maintains young age structure
Concentrates natural enemies (usually more mobile)
Sanitation
Residue removal
Burning
Pruning (Removing Part of a Plant)
Infected/Infested host tissue
Foliage that provides pest access
Alters canopy microclimate
Removing other resources
Varroa Mites – cultural control
Apiary site location
Comb culling
Requeening w/ resistant (tolerant) stock
Varroa Mites – physical control
Screened bottom boards (season long)
Heat (104-110◦F for 4 hrs)
Cultural control in the greenhouse
Inspect new plants thoroughly, reject or discard badly infested ones.
Use fine mesh screening on doors, screens, and ventilators
Use clean or sterile soils or media
Eliminate pools of standing water and any insect breeding debris
Avoid over-watering and promote good ventilation
Thrips IPM
Sanitation
Remove weeds that act as a thrips refuge.
Remove and destroy crop residues after harvest.
Remove all soil debris from greenhouse.
Screen windows, vents, and fans.
Pasteurize soil to kill immature thrips
Which caused by virus?
Yellow fever
Dengue fever
Which caused by bacteria?
Encephalitis
RMSF
Caused by Protozoa
Leishmaniasis
Mosquito vectors for?
Yellow fever Dengue fever Encephalitis W/E equine La crosse Malaria
Ticks vector for?
RMSF
Tularemia
Lyme disease
Sand flies vector for?
Leishmaniasis
Regulatory control
Prevention of pests from entering the country (APHIS)
Rationale
some pests can be excluded by quarantines
cheaper to try and exclude pests than trying to control them
Quarantines only useful for
new pests
Mechanical transmission.
- Facultative
- On mouth parts only (usually)
- Vector must be constantly re-infected
- immediate infectivity
Propagative transmission.
- Obligatory
- Enter insect gut
- Latent period
- Disease titer increases
