Term
|
Definition
| Host where parasite reaches sexual maturity (patent infection) |
|
|
Term
|
Definition
| Host required for parasite maturation, does not reach sexual maturity here |
|
|
Term
|
Definition
| Host not required for parasite maturation, but may provide homeostasis and transport. (e.g., toxocara infection from ingested earthworms/insects) |
|
|
Term
|
Definition
| Life cycle where definitive host is infects another definitive host direcly. CAN use paratenic hosts, but not required. Fecal-oral transmission is one example. |
|
|
Term
|
Definition
Life cycle where parasite is required to pass through an intermediate host to become infective. Definitive host passes egg/larvae to intermediate host --> intermediate host infects another definitive host, where parasite matures.
Vector borne (malaria, HW) or by predator/prey cycle |
|
|
Term
|
Definition
| Eggs pass into into environment and are directly ingested by next definitive host. The parasite egg or oocyst must be able to survive environmental conditions - a paratenic host helps the parasite by providing homeostasis and transport. |
|
|
Term
| Toxocara canis Transmission |
|
Definition
Transplacental AND transmammary
DIRECT w/ possible paratenic (earthworm, snails, rodents, birds) |
|
|
Term
|
Definition
98% of puppies infected by transplacental (after day 40) followed by transmammary
Eggs shed in feces 21 days -3m post partum, then decline
Female parasite produces >200,000 eggs/day, can survive in soil and remain viable >10 yrs
Larva develop inside egg and stay there for protection from environment |
|
|
Term
| Where can children be infected with Toxocara canis? |
|
Definition
| Kids get infected playing in soil, more likely in backyards than parks |
|
|
Term
| What complications does Toxocara canis produce in the human host? |
|
Definition
VLM - nonspecific symptoms (fever, malaise, abdominal pain, leukocytosis and eosinophilia), about 1-5 y/o
OLM - hard to ignore (misdiagnosis common, treated as retrobulbar tumor), about 5-10 y/o. 2nd leading cause of blindness in children |
|
|
Term
| How to prevent VLM and OLM? |
|
Definition
| Deworm puppies at 2, 4, 6, 8 weeks, then start HWP at 10 weeks. Clean feces from YARDS, parks. Do fecals to verify treatments worked. |
|
|
Term
| Use of selamectin in preventing Toxocara canis |
|
Definition
| Parasite preventative useful in gestation - apply to dam at day 40 (before transplacental), apply again at day 10 postpartum to reduce transmammary |
|
|
Term
| Ascarids implicated in migrations |
|
Definition
Toxocara canis
Toxocara cati (yards, sandboxes, counter tops)
Baylisascaris procyonis (raccoons, worse than T. canis, eosinophilic meningitis) |
|
|
Term
| Transmission of Hookworms |
|
Definition
Transmammary
Direct - larvae in environment
Percutaneous - produce collagenase to digest skin |
|
|
Term
|
Definition
| In wrong, larva cannot digest collagen efficiently and wander - painful and irritating. People become infected from contaminated ground or walking barefoot |
|
|
Term
| What meats are associated with Trichinella spiralis? |
|
Definition
|
|
Term
| What is the life cycle of Trichinella spiralis? |
|
Definition
1.) Carnivore ingests meat infected with larvae
2.) Larvae penetrate stomach lining and become adults
3.) Adults mate, females penetrate lining of small intestine and produce larvae (1,000/day for 40-60 days). Intestines act as DH.
4.) Larvae pass through lymphatics, into blood and distributed to musculature
5.) Paralysis develops, infected animal now eaten (IH) |
|
|
Term
| Principal muscles affected by Trichinella spiralis |
|
Definition
| This parasite affects the diaphragm, hypoglossal, and masseter muscles - predator becomes prey |
|
|
Term
| Toxplasmosis infection in cats |
|
Definition
Majority <1 y/o
Majority do not shed oocysts again
FeLV/FIV do not affect shedding - immunosuppression leads to systemic manifestations |
|
|
Term
|
Definition
| Handling raw pork/lamb, tasting marinades, not washing cutting board, feral kittens, unpasteurized milk from actively infected goats |
|
|
Term
| Toxo recommendations to client |
|
Definition
Don't adopt a kitten during pregnancy or chemo
Make cat indoors-only to reduce risk of infection through predation
Don't feed raw scraps to cats
Pregnant women should not scoop litter
Titers on cats are useless - active infection already passed, usually +
FREEZE fresh meat > 48hr |
|
|
Term
| What is the seroprevalance of toxo in the U.S. |
|
Definition
| 30-40% are seroprevalent for this parasite |
|
|
Term
| Tachyzoites & Bradyzoites |
|
Definition
| Stages of toxo in tissue (acute and chronic, respectively) |
|
|
Term
| Characteristics of Toxo Titer |
|
Definition
Most cats + by 1 year old
IgM = recent infection
IgM/IgG = active
IgG = past infection or systemic disease |
|
|
Term
| In NORMAL humans and animals, what do giardia and Crypto usually cause? |
|
Definition
| These parasites usually cause self-limiting diarrhea in normal hosts |
|
|
Term
| Characteristics of Giardia and Crypto |
|
Definition
Infected host can shed 10^6 organisms/gram feces
Infectious dose is very low
Cysts and oocysts resistant to normal municipal water filtration/sewage tx systems
Environmental contamination likely
Commonly affect livestock |
|
|
Term
|
Definition
A and B - potentially zoonotic
C and D - Canid only
E - Hoofstock
F and G - cats, rats |
|
|
Term
|
Definition
Genotype I - C. hominis
Genotyple II - C. parvum, ZOONOTIC |
|
|
Term
| What is a major public health concern with Giardia and Crypto? |
|
Definition
| Water-borne outbreaks (water systems, pools) are a major concern with these parasites |
|
|
Term
|
Definition
Indirect life cycle
An IH is consumed to transmit parasite to DH (dog, cat)
In some cases, parasite debilitates IH to increase likelihood of consumption by DH |
|
|
Term
| How does the tapeworm develop in the IH |
|
Definition
| IH ingests egg -> hatch -> larvae migrate to vital location and form Cysticercus (cysticercoid in arthropod) -> cysticercus enlarges, fills with fluid as space occupying lesion -> IH consumed, develops into adult in DH |
|
|
Term
| What are the parts of a tapeworm? |
|
Definition
Scolex - head (1 per cysticercus)
Strobila - body or bladder. Elongates into proglottids |
|
|
Term
|
Definition
| Humans are DH, cattle are IH, infected by proglottids in feed. Cysticercus in cattle muscle (beef measles), transmitted to human by undercooked/raw beef. |
|
|
Term
|
Definition
| Humans are DH, pigs are IH, infected by proglottids. Humans eat undercooked pork and ingest muscle cysts. If humans consume only eggs, they are the IH. |
|
|
Term
| What is neural cysticercosis? |
|
Definition
| Occurs in humans that act as IH for Taenia solium. Cysts in many sites - brain and eye. Leading cause of adult-onset epilepsy in Mexico. Widespread in tropics, now in US through immigration |
|
|
Term
|
Definition
| Carnivore DH passes egg in feces, no proglottids seen -> herbivore/human IH becomes infected and Hydatid cysts (many scolices) in liver and lungs enlarge to incapacitate the IH slowly |
|
|
Term
| Where is Echinococcus widespread and what host is blamed? |
|
Definition
| In the Middle East, S America, Asia, and Africa, the dog is noted for this zoonotic parasite. Religious taboos against contact with dogs probably stem from this parasite. |
|
|
Term
| Humans serve as DH for which tapeworms? As IH? |
|
Definition
DH for Taenia saginata, Taenia solium
IH for Echinococcusm, Taenia solium |
|
|
Term
| Would it be better to be a DH or IH for a tapeworm? |
|
Definition
| It would be better for the host to be a DH for this parasite, as IH are usually progressively debilitated to the point of death |
|
|
Term
| What is the difference between a zoonotic disease and vector-borne disease? |
|
Definition
Zoonotic diseases are transmissible between different VERTEBRATES
Vector-borne diseases are spread by invertebrates, and may affect multiple species. Can be zoonotic (plague) or non-zoonotic (malaria - man is the only reservoir) |
|
|
Term
|
Definition
Other vertebrates
Passively harbor arthropod-borne disease, must develop high enough blood levels to infect arthropod.
Don't usually die from disease, become sub-clinical carriers |
|
|
Term
|
Definition
Infected host does not develop sufficient pathogen levels to infect arthropod
Ex: white-tail deer carry Lyme but do not infect ticks |
|
|
Term
| What are the 4 genera of Ixodid ticks in North America? |
|
Definition
| Dermacentor (American Brown Dog), Amblyoma, Rhicephalus, Ixodes |
|
|
Term
|
Definition
Adult F lays 5,000 eggs then dies
Eggs hatch into larva, feed on blood-meal (nestling birds, often) and molt into nymphs
Nymphs feed on blood-meal, molt into adults
Adults feed on larger mammals or birds |
|
|
Term
| What is the significance of ticks feeding on neonates? |
|
Definition
| Exposure to a pathogen during immunological development can induce a state of tolerance in neonates whereas exposure of a naive adult would likely kill it. Neonates survive and perpetuate infection. |
|
|
Term
| Transmission of disease in the arthropod |
|
Definition
Transovarian transmission from adult female to eggs
Transtadial - larval stage becomes infected and remains infected through maturation |
|
|
Term
|
Definition
Causative agent: Rickettsia rickettsii
Dermacentor (American Brown Dog tick) are vectors, infected through transtradial AND transovarian
Rodents are reservoirs |
|
|
Term
|
Definition
Humans - acute vasculitis, pettechia, bleeding in many organs (CNS, kidneys), 2-10% mortality
Canine: Vasculitis, hemorrhage, shock, end-arterial organs most affected |
|
|
Term
| Life Cycle of Ixodes (deer tick) |
|
Definition
Adult females preferentially feed on WTD (lay more eggs)
Reservoir is white-footed mouse - transtadial, no transovarian. Larvae feed on neonates
Neonatal white-footed mice infected by nymphal stages |
|
|
Term
| What three organisms must be present for Lyme disease to spread? What can be done to decrease prevalence? |
|
Definition
| Ixodes ticks, WTD, white-footed mice. Rodent control is necessary but not always practical (no reservoir = no disease) |
|
|
Term
| Factors affecting tick-borne illnesses |
|
Definition
-Seasonal and annual variations
-Reservoir capable of transmitting agent
-Environmental factors conducive to reservoir populations |
|
|
Term
| How prevalent is Yersinia pestis today? |
|
Definition
10-20 human cases in US/year
1,000 - 3,000 humans cases worldwide/year - vastly under-reported |
|
|
Term
| Characteristics of Yersinia pestis |
|
Definition
-Facultative anaerobic, intracellular, gramNEG bacillus
-Easy to culture, but survives poorly in environment
-Primarily rodent pathogen - rats, squirrels, prairie dogs
-Kills most rodents it infects, some become carriers |
|
|
Term
| What is the primary vector of Yersinia pestis? |
|
Definition
| Xenopsylla cheopis (oriental rat flea) |
|
|
Term
| Transmission of Yersinia pestis |
|
Definition
| Flea bites infected rodent -> bacillus grows in esophagus/foregut of flea, blocking swallowing -> flea bites again and expels bacteria into new host |
|
|
Term
| Three routes of human exposure to Yersinia pestis |
|
Definition
1.) Flea-borne, from infected rodents
2.) Direct contact with infected tissues or fluids of sick animals
3.) Air-borne by resp droplets from cats and humans with pneumonic plague |
|
|
Term
| What rodent is responsible for the most cases of human plague? What carnivore? |
|
Definition
| When humans are infected, rock squirrels are the most likely rodent source. Cats are the most likely carnivore source. |
|
|
Term
| Three forms of human plaque |
|
Definition
Bubonic - LN are primary site
Septicemic - bacillus has traveled throughout body from bite or LN
Pneumonic - primary site is the lungs |
|
|
Term
| What form of plague do cats spread? |
|
Definition
| Cats spread the pneumonic form - nearly all human pneumonic cases have results from contact with cats. Mortality in both is >50%. |
|
|
Term
| Efforts to control plague |
|
Definition
-Rodent and flea control in environment, flea treatment for dogs and cats.
-Abx if exposed
-No approved vaccine
-No forseeable eradication due to wildlife and flea population |
|
|
Term
|
Definition
| This category includes plague, anthrax |
|
|
Term
|
Definition
Causative agent of Cat Scratch Dz
GramNEG, pleomorphic bacteria
Very slow growing
Sensitive to abx |
|
|
Term
| Epidemiology of Bartonella hensalae in cats |
|
Definition
Cats are main reservoir
Documented in 25-49% of healthy cats
In cats, self-limiting febrile illness of 48 to 72 hours. Produces a chronic, asymptomatic bacteremia for 2m - several years (older cats affected longer than younger)
Transmitted through cat flea, NOT cat-cat or to kittens. (exception: blood transfusion) |
|
|
Term
| Bartonella henselae in other hosts |
|
Definition
Human infection following cat bite/scratch (also, potentially through fleas and Ixodes and Dermacentor)
Immunocompromised dogs may be at risk from Ixodes and Dermacentor |
|
|
Term
| Cat Scratch Disease in humans |
|
Definition
22,000 cases/yr, 2,000 hospital admissions
90% have exposure to cat (other: squirrels, dogs, goats, barbed wire), usually a bite/scratch to head/neck/upper limb
Usually <21 y/o, Sep-March
Usually self-limiting and benign - regional lymphadenopathy, spontaneously resolves in 2-5 m.
Complications possible in immunosuppressed |
|
|
Term
| What disease is associated with Parinaud Ocular Glandular Syndrome? |
|
Definition
| Cat Scratch Disease is associated with this ocular condition in humans |
|
|
Term
| Prevention of Cat Scratch Disease |
|
Definition
1. CONTROL FLEAS
2. Sero-neg cats better for immunocompromised people (e.g., avoid young cats from shelters, etc)
3. Abx tx of bacteremic cats may or may not clear cat of infection |
|
|
Term
| What is the etiological agent of Murine Typhus? |
|
Definition
| Rickettsia typhi causes this illness and is endemic to all continents except Antarctica. It is a gramNEG obligate intracellular bacterium, survives well in environment |
|
|
Term
| Epidemiology of Murine Typhus (Rickettsia typhi) |
|
Definition
Rats are primary host and reservoir - asymptomatic infection.
Vector is primarily Xenopsylla cheopis, infected when feeding on rat -> organism multiplies in mid-gut, infecting flea for life and causing no damage -> shed in flea feces -> rats inhale feces and amplify |
|
|
Term
| Transmission of Murine Typhus to human |
|
Definition
| Man is accidental host, scratching contaminated flea feces into skin. Incubated 1-2w. Also, by cat/mouse flea and direct bite by flea infected >3w. Usually occurs late spring-fall, southern states, in areas with large rat populations. Fever, malaise, headache, joint pain. Tetra/doxycycline. |
|
|
Term
| What are the two types of mosquitoes infected with WNV and what do they feed on? |
|
Definition
Culex - bird feeders
Aedes - mammal feeders |
|
|
Term
| Clinical signs of WNV in the horse |
|
Definition
Acute
93.9% ataxia, usually symmetric
43% CN signs
54% muscle fasciculations
32% fever |
|
|
Term
| Diseases that can resemble WNV |
|
Definition
Rabies (but ascending paralysis)
Botulism (severe muscle shaking)
EPM (asymmetric incoordination) |
|
|
Term
| Vaccine recommendations for WNV |
|
Definition
Regional decision
Horses should receive 2 initial doses 3-6 w apart, before start of mosquito season
Additional booster in July/August if highly stressed |
|
|
Term
|
Definition
Mostly supportive
Anti-inflammatory meds
Mannitol to reduce CNS edema
Antioxidants (Vit E)
IV/parenteral nutrition
Slings/feeding tubes may be necessary |
|
|
Term
|
Definition
CBC/chem WNL
CSF - mononuclear pleocytosis or high TP
Plaque reduction neutralization test is gold standard, but most labs use antigen-capture ELISA for IgM - detected 8-10 days post infection for up to 2m. Virus isolated in whole blood, serum, CSF, CNS |
|
|
