Diagnosis and official regulatory testing for bovine trichomoniasis in
Washington State
What is trichomoniasis?
Bovine venereal trichomoniasis is caused by
Tritrichomonas foetus, a
flagellate protozoan parasite.
T. foetus lives in the reproductive
tracts of bulls and cows and has worldwide distribution. The widespread use of
artificial insemination in many areas of the world has helped to reduce the
prevalence. Trichomoniasis is still of importance in herds where artificial
insemination is not used.
How is trichomoniasis transmitted?
T. foetus is fragile and
cannot survive in the environment (outside the animal). Transmission of the
disease is primarily by sexual contact, but mechanical transmission by
insemination instruments can occur. Venereal transmission can occur from an
infected bull to an uninfected cow (or heifer), or from an infected cow (or
heifer) to an uninfected bull. However, most cows clear the infection
spontaneously and are not significant reservoirs for disease transmission.
Bulls are the main reservoir of the trichomoniasis, and bulls greater than 4
years of age tend to be long-term carriers. For this reason samples from bulls
are preferred for diagnosing and controlling the disease in cattle herds.
What are the clinical signs of trichomoniasis in individual cattle?
Chronically infected bulls show no lesions or clinical disease. Infected bulls
appear normal, breed normally, and can infect an entire herd through natural
service. In the newly infected cow or heifer (in those never before infected
with
T. foetus), there is inflammation of the reproductive tract
(vagina, cervix, uterus), which may result in a discharge from the vagina or, in
severe cases, pyometra (uterus distended with pus and the cow’s inability to
cycle). If the cow is pregnant, the infection results in placentitis
(inflammation of the birth membranes) and causes early abortion (1-16 weeks of
gestation).
How do I know if my cattle herd has trichomoniasis?
A tentative diagnosis of trichomoniasis as a cause of reproductive failure in a
herd is based upon clinical history (presence of clinical signs in individual
cows in a bull bred herd), signs of early abortion, repeated returns to service,
high percentage of unbred cows, and irregular estrus cycles. Confirmation of
trichomoniasis requires demonstration of
T. foetus parasites by
laboratory testing.
How do I get trichomoniasis out of my cattle herd or prevent trichomoniasis
from entering my cattle herd?
Cows with trichomoniasis spontaneously clear
infection in 90-95 days and are not a source of
T. foetus infection
from one breeding season to the next. Bulls become chronically infected with
T. foetus, are long-term carriers and can serve as the source of
trichomoniasis in cattle herds from one breeding season to the next. Thus
control of trichomoniasis in cattle herds requires identification of bulls
infected with
T. foetus by laboratory methods and removal of the
infected bulls from the herd. Also, testing all purchased bulls for
T.
foetus before entering the herd will prevent introduction of trichomoniasis
into your herd. There is no effective method for treating
T. foetus-infected
bulls. Infected bulls are generally culled from the herd and sold for
slaughter.
What samples do I take for laboratory identification
of trichomoniasis?
In cows and heifers,
T. foetus parasites are most reliably identified
from placental fluids, placenta, stomach contents of aborted fetuses, uterine
washings, pyometra discharge, or vaginal mucus. In bulls, preputial smegma is
the optimal sample. If the aborted fetus is recovered, the diagnosis is
relatively easy because of the large number of parasites present in placental
fluids and fetal tissues. Because recovery of fetuses from early abortions
(1-16 weeks gestation) is rare, herd-based diagnosis is usually necessary.
Herd-based diagnosis is most reliably made from preputial scrapings of bulls or
vaginal scrapings/fluids from cows.
How are samples collected for laboratory identification of trichomoniasis?
In non-abortion samples, appropriate sample collection for accurate diagnosis of
trichomoniasis is critical. It is very important to avoid fecal contamination
of the sample because intestinal protozoa and environmental trichomonad
parasites can interfere with growth of T. foetus and can be confused with T.
foetus in laboratory cultures.
In infected bulls, T. foetus parasites
live deep in the preputial folds (microscopic crevices inside the prepuce)
requiring a preputial scraping below the mucosal surface of the prepuce in order
to reach the embedded parasites. The scraping is generally
accomplished with an artificial insemination pipette (dry pipette technique) or
special metal brush.
An online course on Trichomoniasis Testing and a video of the collection
technique in bulls is available at the web link below provided by the Washington
State Department of Agriculture (WSDA) and WSU Veterinary Medicine Extension.
http://vetextension.wsu.edu/programs/bovine/trich/index.htm
How should I store samples for trichomoniasis testing prior to shipping and how
should they be shipped?
All samples submitted to WSU-WADDL should be collected into InPouch TF system
containers, and these should be kept at ambient (room) temperature prior to
shipping to the lab. Ship samples at room temperature by overnight carrier (DO
NOT SHIP WITH ICE PACKS). For small numbers of InPouch TF containers (<10)
contact WADDL (Phone: 509-335-9696-Bacteriology Section). Larger numbers of
pouches can be purchased directly from the supplier listed below.
BioMed Diagnostics
1430 Koll Circle, Suite 101
San Jose, CA 95112-4608
Phone (408) 451-0400
FAX (408) 451-0409
The catalog #s are:
11-1001 InPouch TF-20 (20 pouches)
11-1002 InPouch TF-100 (100 pouches)
Samples for regulatory testing of bulls should be submitted on the WADDL
Trichomoniasis Accession Form. A printable and downloadable version of the
Trichomoniasis Accession Form is available on the WADDL website.
Is specialized training required for collection of samples for laboratory
identification of trichomoniasis?
Yes. The Washington State Department of Agriculture (WSDA) and State
Veterinarian require that veterinarians receive special training, certification
and registration for collection of preputial samples from bulls. Only
veterinarians registered with the WSDA can collect samples for official
trichomoniasis testing in bulls. The WSDA Animal Services Division provides
educational seminars to veterinarians on proper trichomoniasis sampling and
handling techniques. WSDA will recognize other states’ official trichomoniasis
collection protocols when veterinarians outside Washington State collect the
samples.
What are the laboratory tests for trichomoniasis?
T. foetus parasites can be identified in samples by direct microscopic
visualization, culture in specialized growth medium, or polymerase chain
reaction (PCR) detection of parasite nucleic acid (DNA). The sensitivity of
direct detection in bull preputial samples or vaginal samples is not optimal
because the number of parasites is generally low. Better sensitivity is obtained
by amplification of parasite numbers by culture or amplification of parasite DNA
by PCR. Publications comparing the sensitivity and specificity of culture and
PCR vary but both methods perform very well on samples obtained from animals
with clinical signs (near 100%). In samples obtained from animals without
clinical signs of trichomoniasis (for example, carrier bulls) generally PCR is a
more sensitive test than culture. To prove a bull from an infected herd is
uninfected generally requires 3 sequential samples (at least one week apart) if
using culture methods, while only one sample is required if using PCR methods.
For this reason PCR is usually the preferred testing method for official testing
of trichomoniasis in bulls entering Washington State.
What are the Washington State Department of Agriculture (WSDA) regulations
regarding trichomoniasis?
Because bulls with trichomoniasis do not show clinical signs of infection and
because trichomoniasis can cause economic losses to Washington cattle herds
through significant reproductive failure, the WSDA and State Veterinarian
require all breeding bulls entering the state of Washington be shown free of
trichomoniasis. The bovine trichomoniasis requirements are published in
Washington Administrative Code (WAC) document #16-54-086, “Bovine Trichomoniasis
Requirements”.
Briefly, according to
WAC # 16-54-086,
breeding bulls may be imported into Washington if they meet the following
requirements:
- Bulls originate from a herd wherein all bulls have tested negative for
trichomoniasis since removal from female cattle, and the bull (s) being
imported has tested negative within 30 days of import and had no contact
with female cattle.
- Bulls originate from a herd of unknown trichomoniasis status (no animals
laboratory tested for trichomoniasis) but with no know clinical diagnosis of
trichomoniasis, AND the bull being imported is tested negative within 30
days of import and had no contact with female cattle.
- Bulls originate from a trichomoniasis positive herd (by laboratory test
or clinical diagnosis) within the past 12 months, OR originate from a sale
yard, and have 3 consecutive negative culture tests (one week apart) or 1
negative PCR test within 30 days of import.
- All imported, test negative bulls must be identified with official
identification or official trichomoniasis bandle tag.
Bulls entering Washington State without meeting the above requirements will
be quarantined at the owner’s expense until they have 3 consecutive negative
culture tests (one week apart) or 1 negative PCR test.
The State Veterinarian determines trichomoniasis training for veterinarians and
laboratories and the types of tests used to determine infection. A veterinarian
registered by WSDA to perform trichomoniasis testing must collect samples for
trichomoniasis testing in bulls and must submit samples within 48 hours to an
official laboratory. Currently, WSU-WADDL is the only Washington laboratory
recognized by the State Veterinarian for official trichomoniasis testing. WSDA
recommends PCR testing over culture testing because of increased sensitivity of
the PCR test over culture methods, and because the PCR test is more widely
accepted by other states.
Official collection protocols and testing from other states also are acceptable
if approved by the State Veterinarian. Samples must not be exposed to
temperature extremes, and should be kept at room temperature prior to and during
shipping. PCR and culture are both accepted as official trichomoniasis tests.
Samples for regulatory testing of bulls should be submitted on the WADDL
Trichomoniasis
Accession Form
