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HEALTH
RELATED ISSUES
Maternal immunity is the
antibodies kittens get in colostrum in the
first 18-24 hours of life. After that time, they can no longer absorb
large molecules such as antibodies from the gut into the bloodstream.
This phenomenon is called "gut closure" and is a protective mechanism
to prevent the kittens from absorbing bad guys like viruses and
bacteria and toxins. Nursing after 24 hours of age does not provide
further systemic immunity. There is some local activity of
immunoglobulins in the digestive tract, but no further systemic
immunity is acquired. Therefore, age at weaning has no influence on
response to vaccinations.
This passively acquired maternal immunity is designed to protect the
kitten until it starts to make its own antibodies (usually between 4-
6 weeks of age).
If a kitten is vaccinated when it still has high maternal antibody
titres, its own immune system will not respond and make vaccinal
immunity.
Maternal immunity wanes over time at different rates for different
pathogens. Other factors influence waning of maternal immunity, such
as how much maternal immunity the kitten got in the first place, and
individual factors that influence when the kitten starts to produce
its own immunity.
| TRICHOMONOSIS IN CATS CLINICAL
FINDINGS:
Feline T. foetus infection is characterized by a waxing and waning large
bowel diarrhea that occasionally contains fresh blood and mucus. Diarrhea is
semi-formed to cow-pie in consistency and malodorous. In very young cats and
with poor housing conditions, the anus may appear edematous, erythematous and
painful; involuntary dribbling of feces or rectal prolapse may be seen. In
general, cats otherwise maintain good health and body condition. A consistent
feature of T. foetus diarrhea is improved fecal consistency and
disappearance of trichomonads during administration of antimicrobial drugs with
return of diarrhea containing trichomonads shortly after drugs are discontinued.
Misdiagnosis of Giardia is common in cats having T. foetus
infection. Cats diagnosed with Giardia on the basis of direct fecal smear
examination and that fail to respond to appropriate antimicrobial therapy should
be closely re-evaluated for the possibility that the observed trophozoites were
T. foetus.
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PATHOLOGIC FINDINGS:
Hematologic and serum biochemical analysis results from cats with T. foetus
infection are invariably normal. Coexisting enteric infection by recognized
feline pathogens (e.g. Giardia, Cryptosporidium, or internal
parasites) is not a consistent feature. Infected cats usually test negative for
FeLV antigen and FIV antibody. Histopathologic changes in colonic mucosal
biopsies from infected cats have been consistent with mild to severe
lymphoplasmacytic colitis. Because trichomonads are non-invasive and extremely
fragile, they are rarely preserved in intestinal biopsy specimens from infected
cats although immunohistochemistry may be used to enhance their detection.
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DIAGNOSIS:
Direct Fecal Smear Examination:
Diagnosis is made by observation of trophozoites in feces diluted with saline
solution and examined under a coverslip using a 20 or 40x objective. Lowering
the microscope condenser to increase contrast may enhance visualization.
Trichomonad trophozoites must be distinguished from those of Giardia.
Giardia trophozoites have a concave ventral disc and motility reminiscent of
a ¡§falling leaf¡¨. In contrast, trichomonads are spindle-shaped, have an
undulating membrane that courses the entire length of the body and possess a
jerky, forward motility. Tritrichomonas foetus can be difficult to
reliably distinguish from non-pathogenic intestinal trichomonads such as
Pentatrichomonas hominis on the basis of light microscopic appearance as the
two organisms differ in appearance only by the number of anterior flagella.
Fecal samples should be freshly voided and diarrheic. Detection of trophozoites
can be improved by collecting samples using a fecal loop and by examination of
multiple fecal smears. Trichomonads will not survive refrigeration and are not
observed after fecal flotation or sedimentation. Survival of trophozoites in
feces can be extended from 0 to 4 days by removal of adherent litter and
dilution of the sample with normal saline to avoid desiccation (3 ml 0.9% saline
per 2 g of feces). Concurrent antibiotic therapy will diminish the number
trophozoites present in feces, a fact that should be considered in cats with
negative fecal smear results. The sensitivity of direct fecal smear examination
for diagnosis of trichomoniasis is low (2% in cats with experimentally induced
infection and 14% in cats with spontaneous disease).
Fecal Protozoal Culture
If repeated direct microscopic examination results are negative for trophozoites,
feces may be cultured in-house using a commercially-available system marketed
for diagnosis of T. foetus infection in cattle (In PouchTM TF, Biomed
Diagnostics, San Jose CA). For diagnosis of feline T. foetus, pouches
should be inoculated with 0.05 g (about the size of a peppercorn) of freshly
voided or loop-collected feces and incubated at room temperature (25¢XC) in an
upright position. Prior to microscopic examination, pouches are tapped against a
bench-top to dislodge adherent organisms and then placed within a
manufacturer-provided clamp that allows the pouch to be mounted onto the stage
of a light microscope. Pouch contents should be examined every other day for
motile trophozoites using a 20 or 40x objective and discarded if still negative
after 12 days. Fecal culture using In PouchTM TF has a detection limit of >=
1000 T. foetus organisms/0.05 g feces and is superior to direct fecal
smear examination for diagnosis of T. foetus infection. Neither
Giardia nor P. hominis organisms can survive in In PouchTM TF for
longer than 24-hr and thus positive cultures are strongly suggestive of T.
foetus infection. Strictly speaking however, the types of trichomonads
potentially hosted by cats and the specificity of In PouchTM TF with regard to
these other types of trichomonads is unknown. Positive In PouchTM TF cultures do
not preclude the possibility of coinfection with P. hominis or Giardia.
Fecal samples can also be cultured in antibiotic-fortified, modified Diamond¡¦s
medium. Such cultivation requires shipment of feces to a research laboratory,
preparation and maintenance of sterile medium, and 37¢XC incubation and is not
commercially available. There is minimal evidence to suggest that modified
Diamond¡¦s medium culture provides any greater diagnostic sensitivity than
in-house fecal culture using In PouchTM TF.
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