Exam 3 - Vector-borne Diseases Flashcards
when is the overall prevalence of tick infestation highest in the USA?
may & June – second peak in October
what replication-incompetent bacteria relies on fleas & ticks to be transmitted?
bartonella spp.
what protozoal parasite uses an insect as both vector & definitive host?
hepatozoon
what agents are obligate intracellular parasites?
ehrlichia, anaplasma, rickettsia spp.
genus borrelia spirochetes
T/F: obligate intracellular parasites can’t survive outside of the host or vector & therefore, aren’t directly contagious
true – extremely well-adapted to survive
because you typically can’t culture obligate intracellular pathogens to diagnose them, what tests are used instead?
serology or molecular diagnostics
how are infections caused by obligate intracellular parasites treated?
must get drugs into the cells to kill the pathogen – or prevent the transmission in the first place
general tick-borne syndrome involves what agents?
ehrlichia, rickettsia, anaplasma, & borrelia
what is the common presentation of general tick-borne syndrome?
tick was attached for 48 hours or more – clinical signs appear 7-21 days later
what are the common initial signs associated with general tick-borne syndrome?
fever, lethargy, lameness, shifting leg lameness, polyarthritis, polymyositis, acute thrombocytopenia, & may wax/wane in severity
acute signs associated with general tick-borne syndrome are generally rapidly responsive to what antibiotic?
doxycycline
why is shifting leg lameness seen in animals with general tick-borne syndrome?
muscle stiffness, soreness, or pain from systemic inflammatory disease or just achiness
true neutrophilic polyarthritis – may be reactive to systemic inflammatory disease or may be direct spread within connective tissues
what 3 mechanisms are associated with acute thrombocytopenia in animals with general tick-borne syndrome?
- increased consumption – fever, inflammatory cascade during bacteremia/parasitemia, vasculitis
- concurrent immune-mediated destruction in some cases – could be specific or bystander
- impaired function also likely – bleeding occurs at platelet counts higher than typically seen with spontaneous bleeding
T/F: anemia is a common feature of general tick-borne syndrome
false – but when present, anemia of chronic inflammatory disease & is non-regenerative
what major clinical syndromes are associated with vector-borne diseases in humans?
spotted fever group, STAR, tick-borne relapsing fever (borrelia turicatae), r. typhi, & r. prowazekii
what is the primary vector of rickettsia rickettsii?
dermacentor species
what are the possible reservoirs for rickettsia rickettsii?
dermacentor, small mammals, rodents, & birds
where is the highest seropositivity of dogs with rickettsia rickettsii?
eastern time zones
where are human cases of rocky mountain spotted fever most prevalent?
southeast united states
rickettsia rickettsii causes clinical disease in what species?
dogs & people
what are the target cells of r. rickettsii?
vascular endothelial cells – ‘spotted’ appearance
typically, mild thrombocytopenia – likely immune-mediated or secondary to vasculitis
diffuse vasculitis often progresses to DIC
what is the prognosis of rocky mountain spotted fever?
acute disease only!!!
dead or better in days to weeks – extremely rapidly treatment responsive
T/F: in rocky mountain spotted fever, exposure-induced immunity is protective for 3 years or more
true
what ticks transmit ehrlichia canis?
r. sanguineus & d. variabilis
what serves as the reservoir for e. canis?
wild & domestic canids
why is ‘canine monocytotropic ehrlichiosis’ another name for e. canis infections?
monocytes/macrophages are the preferred target cells
what are the 3 phases seen with e. canis infections?
- acute – 2-4 weeks, thrombocytopenia, multisystemic signs
- subclinical – months to years to indefinitely (splenic hideout), may remain mildly thrombocytopenic
- chronic – pancytopenia
when are specific IgM & IgG antibodies seen in e. canis infections?
IgM by 4-7 days post-infection
IgG by 15 days post-infection
T/F: antibodies for e. canis are not protective
true
what are some possible vectors for ehrlichia chaffeensis?
amblyomma, dermacentor, ixodes, & haemaphysalis
what are some possible reservoirs for ehrlichia chaffeensis?
white tail deer, possums, coyotes, raccoons
ehrlichia chaffeensis causes clinical disease in what species?
people & dogs
what are the target cells of ehrlichia chaffeensis?
monocytes & neutrophils – perhaps more uveitis seen, milder than e. canis but similar disease
what is the only proven vector of ehrlichia ewingii?
amblyomma americanum
what is the reservoir of ehrlichia ewingii?
white tailed deer
ehrlichia ewingii causes disease in what species?
dogs & people
what is another name for ‘ehrlichia ewingii’?
canine granulocytotropic ehrlichiosis – target cells are neutrophils & eosinophils
visually looks like a. phagocytophilum
where is anaplasma phagocytophilum especially common?
northern midwest USA
what tick species transmits anaplasma phagocytophilum?
ixodes
what are the reservoirs of anaplasma phagocytophilum?
small mammals & deer
anaplasma phagocytophilum causes clinical infection in what species?
dogs, horses, & people
what is the target cell of anaplasma phagocytophilum?
neutrophils
what are the common clinical abnormalities of an animal with anaplasma phagocytophilum?
acute illness with notable lameness – muscular pain and/or neutrophilic polyarthritis
typically, low platelets & low eosinophils
antibody titers persist but don’t protect against re-infection
what is the suspected vector of anaplasma platys?
r. sanguineus
anaplasma platys causes clinical disease in what species?
dogs
what disease does anaplasma platys cause?
infectious cyclic thrombocytopenia – 1–2-week cycle of platelet parasitism, clearance & drop in count (<20K)
only 1% of platelets are parasitized – platelet clearance must include immune-mediated component
what ticks transmit borrelia burgdorferi?
ixodes species & amblyomma
why is it important to know borrelia burgdorferi has many reservoirs?
many reservoirs mean ticks can become infected as larvae, nymphs, or adults
what reservoirs are important for larvae & nymphs when considering borrelia burgdorferi? what about adults?
rodents, small mammals, lizards
adults – deer, large mammals, & lizards
borrelia burgdorferi causes clinical disease in what species as hosts of adult ticks?
dogs & people
how is the lifecycle of ixodes tick species different in the south from the north?
we have lizards who are cold blooded & can’t amplify disease well, so lower prevalence of lyme
in endemic areas of b. burgdorferi, many dogs & people are exposed, but there are few clinical cases of disease – why?
takes»_space; 24 hours to infect after tick attachment & also likely natural host resistance
what are the clinical signs of b. burgdorferi infections?
direct migration through connective tissues
fever, malaise, polyarthritis, typically acute, self-limiting but some poorly understood chronic immune-mediated complications leading to severe protein-losing nephropathy in certain dogs
how is b. burgdorferi treated?
antibiotics – very responsive
what is the disease process of lyme nephritis?
severe membranoproliferative glomerulonephritis causing severe proteinuria that is associated with lyme seropositivity
T/F: lyme nephritis is a direct result of lyme infection
false – it is an immune-mediated disease
what major clinical signs are associated with r. rickettsii?
high fever, acute severe illness, & often petechiae
what major clinical signs are associated with a. phagocytophilum?
often subclinical, can show fever, lethargy, & shifting leg lameness
what major clinical signs are associated with e. canis (acute)?
fever, acute moderate illness, shifting leg lameness, & rare petechiae
what major clinical signs are associated with b. burgdorferi?
often subclinical, delayed, can have a fever, shifting leg lameness, no human target lesions!!
what is the primary reservoir & definitive host of hepatozoon americanum?
a. maculatum
what is the accidental host of hepatozoon americanum? how does transmission occur in this fashion?
dog is the accidental host – dog must eat the tick for transmission to occur
what is the pathogenesis of hepatozoon americanum?
sporozoites escape gi tract into blood/lymphatics & travel in unidentified host where it then lodges in skeletal & cardiac muscle causing cysts
cystic structures either go dormant or become merozoites
what can be seen on histopathology in hepatozoon americanum infections? what about a blood smear?
cysts easily seen on histopathology
merozoites occasionally seen in circulation
hepatozoon americanum causes clinical disease in what species?
dogs only
what clinical signs would cause suspicion of hepatozoon americanum infections?
cachexia, progressive wasting illness, painful gait, mucopurulent ocular discharge, outrageous leukocytosis, & periosteal reaction
what species of bartonella uses fleas as a vector?
b. henselae
what species of bartonella uses ticks as a vector?
b. vinsonii subspecies berkhoffi
b. henselae is adapted to what species?
cats - rarely makes them sick
b. vinsonii subspecies berkhoffi is adapted to what species?
coyotes – occasionally makes dogs sick
T/F: each species of bartonella is highly adapted to a preferential mammalian host in which they cause a long lasting intra-erythrocytic bacteremia
true
what are the 4 koch postulates?
- microorganism must be found in abundance of all organisms suffering from the disease but should not be found in healthy organisms
- microorganism must be isolated from a diseased organism & grown in pure culture
- cultured microorganism should cause disease when introduced into a healthy organism
- microorganism must be re-isolated from the inoculated, diseased experimental host & identified as being identical to the original specific causative agent
why are bartonella species considered to be the ideal parasite?
various species coadapted with hosts & vectors over evolutionary time
stimulates minimal immune attack
persists in relatively low but stable numbers inside RBCs
causes minimal disease in host
readily transmitted by common routes or blood
features that make it difficult for science & medicine to detect
what are the target cells of bartonella species in mammalian hosts?
RBCs & endothelial cells
bartonella species cause clinical disease in what species?
dogs, cats, & people
what clinical signs are associated with bartonella infections?
pyogranulomatous lymphadenitis, peliosis/vasculoproliferative lesions, endocarditis/meningitis/encephalitis/retinitis/recurrent fever
what is the pathogenesis of babesia?
direct hemolysis causing a profound anemia, mild thrombocytopenia, & potential for severe systemic disease
what tick transmits b. canis?
rhipicephalus, dermacentor
what babesia is the classic strain? what is its appearance?
b. canis vogeli - larger, single or paired, piriform shape
what animals are predisposed to b. canis vogeli?
greyhounds & splenectomized dogs
what animals are predisposed to b. gibsoni?
pitbulls & splenectomized dogs
what is the newer strain of babesia?
b. gibsoni - smaller, usually single, pleomorphic in appearance
how is b. gibsoni transmitted?
suspected transplacental & blood to blood transmission
what is seen on this blood smear?
b. canis vogeli
what is seen on this blood smear?
b. gibsoni
T/F: immunosuppression (splenectomized patients) can exacerbate clinical presentation of babesia
true - if spleen is present, likely to be enlarged
what babesia strains usually cause a mild, chronic, insidious usually extravascular hemolysis?
b. canis strains in the US & b. gibsoni
what babesia strains usually cause a peracute severe intravascular hemolysis?
b. canis in africa & b. gibsoni in USA
what are the presumed vectors & transmission of hemotropic mycoplasma species?
flea in cats & tick in dogs are presumed - direct blood to blood contact may also be a source of transmission
what are the hemotropic mycoplasma species in dogs & cats?
mycoplasma hemofelis in cats
mycoplasma hemocanis in dogs
what disease do hemotropic mycoplasma species cause in dogs & cats?
hemolytic anemia in cats & splenectomized dogs that may be severe or cyclic in times of stress/pregnancy
what is the definitive host & main vector of cytauxzoon felis?
a. americanum - definitive host & main vector
what is the reservoir host of cytauxzoon felis in the midwest & east US?
bobcat
what is the incubation period of c. felis?
2 weeks
what is the terminal phase of disease associated with cytauxzoon felis?
survivors develop piroplasms in RBCs causing hemolysis
what is the pathogenesis of cytauxzoon felis?
sporozoites invade mononuclear cells in circulation where they undergo schizogony where large numbers of schizonts are produced
bloated, infected cells clog capillaries & result in multi-organ failure & death
what agent is seen on this histopath sample?
cytauxzoon felis
when would you do a muscle biopsy for a presumed vector-borne disease?
hepatozoon infections - to visualize cysts on muscle bopsy or circulating gamonts in neutrophils
what is seen on this muscle biopsy?
hepatozoon cyst
what is seen in the neutrophils?
gamonts of hepatozoon
what disease would you use IFA detection for organisms in skin lesions?
rocky mountain spotted fever
what disease would you enrich a sample by growth on insect media, and then perform a PCR?
bartonella species
what is the therapy used for treating ‘challenging’ hepatozoon?
triple therapy - TMS, clindamycin, & pyrimethamine for the first 14 days & coccidiostat for life
what is the therapy for bartonella infections?
long-term doxycycline, enrofloxacin, azithromycin, & rifampin
what therapy is used to treat babesia canis?
imidocarb
what therapy is used to treat babesia gibsoni?
azithromycin/atovaquone
what therapy is used to treat cytauxzoon felis?
azithromycin/atovaquone
flea preventatives protect animals from what agents?
bartonella & mycoplasma
tick preventatives protect animals from what agents?
rickettsia, ehrlichia, anaplasma, babesia - kills the ticks before engorgement & transmission
not eating raw salmon prevents what disease?
neorickettsia
no eating ticks helps prevent what disease?
hepatozoon
no fighting with pitbulls prevents what disease?
babesia gibsoni
what lyme vaccine is available for dogs?
recombinant osp A - expressed on borrelia in tick, so anti-osp a antibodies in dog blood kill borrelia in tick before transmission
what is included in genera; tick-borne disease therapy?
doxycycline for: ehrlichia, rickettsia, anaplasma, borrelia, mycoplasma
fluid therapy for fever, prevent dehydration from malaise/anorexia/painful ambulation
consider NSAIDS for fever & joint pain if hydrated
optimal duration of therapy is uncertain because clinical signs improve quickly but not always certain that the pathogen is fully eradicated
a 5 y/o lab has a positive 4DX snap test for anaplasma species at the time of his annual exam. What does this mean?
positive for antibodies to anaplasma - may not be an ongoing infection, can still treat
a 5 y/o lab has a positive 4DX snap test for anaplasma species at the time of his annual exam. What does this mean? How does your answer change if the dog is sick with a fever, shifting leg lameness, & mild thrombocytopenia?
give it doxycycline - suggests active problem
what agents does a 4DX snap test look for?
ehrlichia canis or chaffeensis antibodies
anaplasma phagocytophilum or platys antibodies
borrelia antibodies against C6 antigen
heartworm antigen
T/F: RMSF has a high background in endemic areas
true
T/F: bartonella also has a very high background seropositivity, so most chronic cases were never sick
true
T/F: in RMSF, there is acute disease only, so convalescent titers rise after recovery
true
what is serology?
study of serum
the presence of antibodies in the serum means that the pathogen has been there, but what is unclear?
not clear when the animal had the pathogen
not clear if the pathogen made the animal sick then or now
T/F: patient side tests for vector-borne diseases don’t reveal the magnitude of disease
true
what historical or physical examination findings may help you recognize infection with ehrlichia species?
*
what historical or physical examination findings may help you recognize infection with hepatozoon?
*
what historical or physical examination findings may help you recognize infection with rickettsia rickettsii?
*
what is the life cycle of neorickettsia species?
n. helminthoeca infects the fluke
fluke infects snail & reproduces
fluke progeny directly penetrate & infect fish
dog eats fish infected with flukes that are infected with n. helminthoeca
what is the agent that causes potomac horse fever?
neorickettsia risticii
what are the target cells of neorickettsia helminthoeca?
monocytotropic & enterocytotropic
what is the agent that causes salmon poisoning?
neorickettsia helminthoeca
what is neorickettsia helminthoeca?
regionally restricted trematode vectors that are infected with neorickettsia species
how is neorickettsia helminthoeca diagnosed?
assisted by the presence of trematode ova in feces of a sick dog
what is a one-host tick? two-host? three-host?
one host - one individual through all life stages
two host - two individuals, +/- 2 species
three host - 3 individuals, up to 3 species
what does transstadial mean?
between life stages
what does transovarial mean?
between generations
what does ixodid mean?
family of all hard ticks
what agent has the cell target of platelets?
anaplasma platys
what is this tick?
rhipicephalus sanguineus - brown dog tick
what is this tick?
rocky mountain wood tick or american dog tick - dermacentor andersoni, d. variabilis
what is this tick?
‘deer ticks’
what is this tick?
lone star tick, gulf coast tick - amblyomma americanum, a. maculatum
how does the need for a vector impact epidemiology, diagnosis, or treatment of these infections?
*
what agents are involved in causing general tick-borne syndrome?
ehrlichia, rickettsia, anaplasma, & borrelia
