Twelve Eimeria spp have been identified in the feces of cattle worldwide, but only 3 (E zuernii, E bovis, and E auburnensis) are most often associated with clinical disease. The other Eimeria spp have been shown experimentally to be mildly or moderately pathogenic but are not considered important pathogens.
Coccidiosis is commonly a disease of young cattle (1–2
mo to 1 yr) and usually is sporadic during the wet seasons of the year.
“Summer coccidiosis” and “winter coccidiosis” in range cattle probably
result from severe weather stress and crowding around a limited water
source, which concentrates the hosts and parasites within a restricted
area. Although particularly severe epidemics have been reported in
feedlot cattle during extremely cold weather, cattle confined to
feedlots are susceptible to coccidiosis throughout the year.
Outbreaks
usually occur within the first month of confinement. Cows may contribute
to environmental contamination of E bovis oocysts through a periparturient increase in fecal oocyst counts. Time to onset of diarrhea after infection is 16–23 days for E bovis and E zuernii and 3–4 days for E alabamensis;
clinical disease due to coccidiosis does not typically occur in the
first 3 wk of life. Coccidiosis is therefore not considered part of the
neonatal diarrhea complex in calves.
Severe infections are rare. Severely affected cattle develop thin,
bloody diarrhea that may continue for >1 wk, or thin feces with
streaks or clots of blood, shreds of epithelium, and mucus. They may
develop a fever; become anorectic, depressed, and dehydrated; and lose
weight. Tenesmus is common because the most severe enteritis is confined
to the large intestine, although pathogenic coccidia of cattle can
damage the mucosa of the lower small intestine, cecum, and colon. During
the acute period, some calves die; others die later from secondary
complications (eg, pneumonia). Calves that survive severe illness can
lose significant weight that is not quickly regained or can remain
permanently stunted. Calves with concurrent enteric infections (eg, Giardia)
may be more severely affected than calves with coccidia infections
alone. In addition, management factors, such as weather, housing,
feeding practices, and how animals are grouped, are important in
determining the expression of clinical coccidiosis in cattle.
Nervous signs (eg, muscular tremors, hyperesthesia, clonic-tonic
convulsions with ventroflexion of the head and neck, nystagmus) and a
high mortality rate (80–90%) are seen in some calves with acute clinical
coccidiosis. Outbreaks of this “nervous form” are seen most commonly
during, or following, severely cold weather in midwinter in Canada and
the northern USA; there are no reports of the “nervous form” outside
this geographic location. Affected calves may die <24 a="" after="" and="" be="" been="" calves="" clinical="" coccidiosis.="" coccidiosis="" commonly="" days="" degree="" dysentery="" even="" experimental="" for="" have="" hr="" in="" indeed="" laterally="" live="" may="" mild="" nervous="" not="" of="" onset="" opisthotonos.="" or="" p="" position="" recumbent="" reported="" several="" signs="" suggests="" that="" the="" they="" to="" unrelated="" which="" with="">
Diagnosis of coccidiosis is by finding oocysts on
fecal flotation or direct smear or by the McMaster's technique.
Quantitative oocyst counts on individual rectal samples from at least 5
calves in a pen are helpful in confirming coccidiosis as a cause of
clinical disease. Differential diagnoses include salmonellosis, bovine
viral diarrhea, malnutrition, toxins, or other intestinal parasites.
Coccidiosis is a self-limiting disease, and
spontaneous recovery without specific treatment is common when the
multiplication stage of the coccidia has passed.
Drugs that can be used for therapy of clinically
affected animals include sulfaquinoxaline (6 mg/lb/day for 3–5 days) and
amprolium (10 mg/kg/day for 5 days). Sulfaquinoxaline is particularly
useful for weaned calves that develop bloody diarrhea after arrival at a
feedlot. For prevention, amprolium (5 mg/kg/day for 21 days),
decoquinate (22.7 mg/45 kg/day for 28 days) and lasalocid (1 mg/kg/day
to a maximum of 360 mg/head/day), or monensin (100–360 mg/head/day) can
be used. The major benefits of coccidiostats are through improved feed
efficiency and rate of gain.Also combination of Trimethoprim and Sulpha drug is good.
Control of infection should include changes in management factors that
contribute to the development of clinical disease. Inadequate housing
and ventilation should be corrected, feeding practices adopted that
avoid fecal contamination of feed, calves grouped by size, and an
“all-in/all-out” method of calf movement from pen to pen adopted.