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Cryptosporidiosis is a protozoal
disease that is similar to coccidiosis in several ways. Protozoa
are one-celled animals and most kinds are harmless. But several
types cause disease in animals and most of these are transmitted
by the fecal-oral route; the protozoa are passed in the feces of
an infected animal and are ingested by a susceptible animal via
contaminated feed or water or when licking a dirty hair coat or
suckling a dirty udder. The
protozoa that cause cryptosporidiosis are found almost
everywhere. Various types infect humans, sheep, goats, deer,
squirrels, etc. but only one type infects cattle. This same type
can also infect humans. Another strain affects only humans.
Several strains affect humans and various other animals but not
cattle. Wildlife such as raccoons occasionally pass crypto to
livestock.
These protozoa survive in moist
conditions and can live for about 170 days in streams of water.
They can also live on wet, contaminated calving grounds, but
drying or freezing will eventually kill them. After being
ingested, they multiply in the calf’s intestine, causing
diarrhea. It’s rare to find this pathogen in calves older than 4
months old or in adults, but many beef and dairy calves are
infected during their first months of life.
In earlier years, this disease
was a problem only in dairy cattle and was estimated to affect
up to 70 percent of dairy calves 1 to 3 weeks of age, with rate
of infection on some farms as high as 100 percent. Now, however,
this disease appears in beef herds as well. Though cryopto is
often mild and self-limiting (runs its course without treatment
and the animal recovers), it can be life threatening in any
human or young animal with a compromised immune system or
concurrent illness with some other disease.
In one study, 5 percent of cows
tested were carriers, spreading a few protozoa continually in
their feces. Thus these organisms are fairly common in the
environment and in the water, on certain farms or ranches. The
best defense against crypto is a healthy herd in good condition,
in a clean environment. Herd health can be compromised by
improper nutrition, so whenever you are dealing with crypto you
also want to take a hard look at the trace mineral status of
your animals—especially selenium and copper, since they are
crucial to a strong immune system and seem to be especially
important in whether or not cattle are susceptible to crypto.
This disease can be deadly if
young calves are challenged with several pathogens at once, such
as bacterial and/or viral scours along with the protozoa. Calves
with severe, hard-to-treat diarrhea usually have mixed
infections. Once you’ve had crypto on your place and the
environment is contaminated, it is almost impossible to get rid
of it. Each new crop of calves may become infected. Thus the
best defense is a healthy herd, to keep animals from becoming
sick with crypto in the first place.
The Disease
The life cycle of cryptosporidia is different from that of
coccidiosis. With coccidiosis, calves don’t break with diarrhea
until they are at least 3 weeks old. By contrast, a calf with
crypto can develop diarrhea as young as 4 days of age if he was
born in a contaminated place and ingests a large number of
protozoa soon after birth. After an oocyst is ingested, it
attaches to the intestinal lining to sporulate and multiply,
similar to the multiplication stages of coccidia, but the
incubation time for crypto is only 2 to 7 days. Thousands of new
oocysts are then passed in the feces for 3 to 12 days. Infection
persists until the calf develops enough immune response to
eliminate the parasite from the body.
When protozoa attach to the
intestinal lining, white blood cells migrate to the site to
fight off the infection, creating intense inflammation. The only
way the calf can get rid of the pathogen is to get rid of the
cell it’s attached to, so the lining is shed. The raw gut can no
longer absorb fluid and nutrients, so everything shoots on
through, creating watery diarrhea.
Peak diarrhea occurs about 3 to 5
days after the calf ingests oocysts. The gut usually heals in a
few days, but without intensive supportive treatment some calves
will die from dehydration before the gut heals. Calves younger
than 3 weeks of age usually take longer to regenerate damaged
gut lining than an older calf, and the young ones also dehydrate
more quickly.
Just like coccidiosis, after a
calf gets over the infection he has some resistance. Even if he
encounters the crypto protozoa again, he’s less likely to get
sick again but may continue to shed a few oocysts. Adult cattle
usually don’t become ill with crypto but can serve as a source
of infection for calves.
Symptoms
Calves with crypto usually have diarrhea, which persists for
several days even if you treat them, since protozoa do not
respond to antibiotics. The feces are usually watery, pale or
greenish in color, but sometimes yellow, cream-colored or gray.
The fluid feces do not contain blood because the damage is not
that deep (in contrast to the bloody diarrhea of coccidiosis).
You may see mucus or shreds of
tissue in the feces. The calf may be dull and not nursing. He
may be dehydrated and/or show signs of gut pain. Persistent
diarrhea may result in weight loss and emaciation. If
complicated by concurrent infection with bacteria or viruses,
the calf is usually much sicker. It may take diligent nursing
care and frequent administration of fluids to keep him alive
long enough for the gut to heal.
Treatment
There’s no specific medication for crypto available on the
market. Supportive care (fluids, electrolytes and good
nutrition) can often save the calf if started early. If the calf
is not nursing, he should be force fed milk or milk replacer as
well as extra fluids, or he may become weak. Studies have shown
that Banamine is also helpful, to reduce inflammation and to
make the calf less miserable—so he’ll be more apt to keep
nursing his dam. IV fluids may be necessary for calves that are
unable to absorb oral fluids.
Prevention
Make sure you never bring this bug to your place if you
don’t have it already. Since it’s a common problem in dairy
calves, don’t buy dairy calves to raise on bottles or nurse
cows, or to graft on beef cows that have lost their own
calves—unless you are very sure the dairy calves are healthy and
have never been exposed to crypto. Even if they look healthy,
isolate them for 5 days after you bring them home, to be sure
they are not incubating the disease. Then if they develop
diarrhea you can clean up the isolation pen and haven’t exposed
other calves. Don’t buy cows (beef or dairy) from any herd or
farm known to have crypto.
If this disease is already on
your place, keep all calving cows and young calves in a clean
environment, so calves won’t be exposed early in life by
ingesting protozoa with contaminated feed or water, or nursing a
dirty udder. If a pregnant cow lies in dirty bedding or on
contaminated ground, she may get feces on her udder and the calf
may ingest oocysts with his first nursing. The same precautions
should be taken as for preventing spread of coccidiosis.
There is no vaccine that is very
effective to prevent crypto, though researchers have been
working on this. Control depends on cleanliness, avoidance of
stress and crowding, and making sure cattle have clean feeding
and bedding areas. Feeding areas should be continually moved to
clean ground, if you are using round bale feeders or spreading
hay on the ground.
Isolate any calf that develops
diarrhea. Bring the cow and calf out of the herd to a “sick pen”
so the calf won’t spread oocysts and infect other calves. Keep
them separate from the herd for several days after the calf
recovers. Be sure YOU don’t transmit the disease to other
animals. Change clothes and footwear or rinse your boots in a
disinfectant solution, wash your hands, and don’t track feces
from the sick pen to other locations.
Make sure every calf on your
place gets adequate colostrum soon after birth. Even though cows
don’t produce many antibodies against protozoa, they produce
some if they’ve been exposed to crypto, and this may give their
calves some protection. In trials with crypto, the calves that
had adequate colostrum were more difficult to intentionally
infect with this disease. Healthy, unstressed calves with high
levels of antibodies from colostrum also won’t develop other
diseases that might put them at risk for a serious case of
cryptosporidiosis.
BE CAREFUL HANDLING SICK CALVES
Cryptosporidiosis can be spread from calves to humans. Calves or
humans in good health can usually handle exposure and not become
ill. Very young calves or humans, or elderly people, or anyone
with a compromised immune system may become seriously ill,
however. Crypto can cause devastating illness in vulnerable
people or calves, such as calves that did not get colostrum at
birth. Be careful when treating sick calves so you don’t
inadvertently spread the disease to a vulnerable human. Wash
your hands and change your clothes when you come indoors,
especially if you have young children or elderly adults in your
home. |
