Evaluation of lasalocid as a coccidiostat in calves: titration, efficacy, and comparison with monensin and decoquinate

Two experiments were conducted to evaluate lasalocid as a coccidiostat in Holstein calves and to compare lasalocid with monensin and decoquinate. In experiment 1, calves in 3 groups (6 calves/group) were each inoculated with 500,000 sporulated oocysts, 88% of which were Eimeria bovis and 12% were E zuernii. Calves in each group were given lasalocid-medicated feed at 0.50 (group 3), 0.75 (group 4), or 1 mg/kg (group 5) of body weight/day for 45 days. Two control groups (6 calves/group) were also evaluated; calves in control group 2 were inoculated and nontreated, and calves in control group 1 were noninoculated and nontreated. At 0.50, 0.75, or 1 mg/kg/day, lasalocid was equally effective in preventing induced coccidiosis (E bovis and E zuernii) in calves. Compared with inoculated nontreated controls, treated calves had significantly (P less than 0.05) fewer oocysts in feces and had fewer clinical signs of coccidiosis from days 16 to 30 after inoculation. Experiment 2 was conducted to compare the effectiveness of monensin, lasalocid, and decoquinate for the prevention of experimentally induced coccidiosis. Calves (n = 48) were allotted into 4 groups (12 calves/group); each was inoculated orally with 275,000 sporulated oocysts, predominantly E bovis and E zuernii, and each was given nonmedicated feed (group 6) or feed medicated with 33 mg of lasalocid (group 7), decoquinate (group 8), or monensin (group 9)/kg of feed for 46 days. Calves given medicated rations had significantly (P less than 0.05) fewer oocysts in their feces and fewer clinical signs of coccidiosis than did calves given nonmedicated rations.(ABSTRACT TRUNCATED AT 250 WORDS)     

The development of eimerian infections during the first eight months of life in unweaned beef calves in a dry tropical region of Australia

The development of coccidial infections in 21 free-ranging, unweaned beef calves from birth to 8 months was investigated by examining faecal samples for oocysts. Most calves commenced shedding oocysts within a month of birth, and had shed all nine species identified by 3-4 months. Oocysts were shed by three calves as young as 12 and 13 days. The oocysts species shed earliest, and the commonest thereafter, were Eimeria bovis, E. ellipsoidalis and E. zuernii. Although several oocyst counts between 5.0 X 10(3) and 114.0 X 10(3)g-1 of faeces of these potentially pathogenic species were recorded there was no clinical disease. Some calves shed oocysts approximately four times more frequently than others, and individual species counts greater than or equal to 5.0 X 10(3)g-1 were confined to 10 of the calves. Intermittent oocyst shedding continued throughout the study with a similar distribution of oocyst species from all calves.     

Prophylactic use of decoquinate for infections with Cryptosporidium parvum in experimentally challenged neonatal calves

OBJECTIVE: To evaluate the effect of daily oral administration of decoquinate to neonatal calves experimentally challenged with various numbers of Cryptosporidium parvum oocysts. DESIGN: Clinical trial. ANIMALS: 75 calves. PROCEDURE: Calves were purchased from a commercial dairy during a 5-week period. Calves were housed in individual hutches and fed milk replacer with or without decoquinate (2 mg/kg [0.9 mg/lb per day]). Calves were randomly assigned to treatment and 1 of 5 challenge groups (0, 50, 100, 1000, or 10,000 C. parvum oocysts in 60 mL of saline [0.9% NaCl] solution administered p.o. on the day after arrival). Calves were maintained in the study for as long as 28 days. Calves were clinically assessed for diarrhea and dehydration. Fecal samples were submitted for oocyst enumeration 3 times each week. RESULTS: Treatment did not affect number of days to first watery feces (diarrhea), number of days to first oocyst shedding, or duration of diarrhea or oocyst shedding. Duration of oocyst shedding was significantly associated with challenge dose of oocysts administered to calves and number of days to first oocyst shedding. Duration of diarrhea and number of days to first oocyst shedding were significantly associated with week of arrival and number of days to first watery diarrhea. CONCLUSIONS AND CLINICAL RELEVANCE: Daily treatment with decoquinate at the dosage used in this study did not affect oocyst shedding or clinical signs associated with cryptosporidiosis. However, there was an indication that if the number of oocysts calves received could be reduced, then the duration of oocyst shedding and, hence, environmental loading of C. parvum oocysts could be reduced.     

Control of bovine coccidiosis with monensin: in nonresistant newborn calves

Newborn Holstein male calves were purchased within 3 days after birth and were removed from the local farms to the Dixon Springs Agricultural Research Center. They were hand-fed for 7 weeks and then weaned to a prepared feed. Eight groups, each of 4 calves, were housed in separate pens. In each of 4 pens (pens 2 to 5), 1 calf was inoculated with sporulated oocysts of Eimeria bovis (and was not medicated); 1 calf was inoculated and given feed with added monensin at the dosage level of 10 g/906 kg of feed; and 2 calves were inoculated and given medicated feed with added monensin at the dosage level of 20 g/906 kg or 30 g/906 kg. In the 4 other pens (6 to 9), the calves were inoculated with E zuernii and otherwise were given feed without or with added monensin as in pens 2 through 5. Another group of 5 calves (all kept in 1 pen), served as noninoculated, nonmedicated controls. At 14 days after inoculations with E bovis, the single calves in each of the 4 pens that were given the nonmedicated feed began to show clinical signs of coccidiosis and discharged increasing numbers of oocysts. The other inoculated calves (given monensin) had fewer clinical signs and discharged fewer oocysts in the feces as the level of medication in the feed increased. The calves inoculated with E zuernii developed only moderately severe infections when compared with those inoculated with E bovis. Inoculated (with E bovis) nonmedicated calves had severe reductions in feed consumption and weight, and 3 of 4 died.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of intermittent and continuous administration of decoquinate on bovine coccidiosis in male calves

Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given decoquinate (0.5 mg/kg of body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of decoquinate/kg every 3rd day discharged more oocysts and had more diarrhea than did calves given 1 mg of decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given decoquinate were mostly normal. Apparently, reduced infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia. Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of decoquinate/kg every 2nd day or 1.5 mg of decoquinate/kg every 3rd day, oocyst production was reduced and clinical coccidiosis was prevented.     

Efficacy of salinomycin in treatment of experimental Eimeria bovis infections in calves

The efficacy of salinomycin for treatment of experimental Eimeria bovis infections was evaluated. In experiment 1, 18 calves were placed into four groups. Group 1 calves were nonmedicated controls; groups 2, 3, and 4 calves were given salinomycin (0.33, 0.66, and 1.00 mg/kg of body weight, respectively) in daily oral divided doses starting 2 or 3 days prior to E bovis inoculations and continuing until postinoculation day (PID) 21. Calves treated with 0.66 and 1.00 mg/kg (groups 3 and 4) passed substantially fewer oocysts than did control calves (group 1) or calves treated with 0.33 mg/kg (group 2). Group 1 control calves had typical signs of severe E bovis infections, whereas signs of infection in medicated calves were almost nonexistant. Experiment 2 was conducted as before, with 15 calves. Group 5 calves were nonmedicated controls; groups 6, 7, and 8 calves were treated with 0.5, 1.0, and 2.0 mg/kg, respectively. All group 8 calves and three of four group 7 calves had nearly complete suppression of oocyst excretions. The severity of the disease in the group 5 control calves was not as extensive as it was in group 1 control calves. In experiment 3, 16 calves were used. Group 9 calves were nonmedicated controls, whereas other calves were given salinomycin (2.0 mg/kg) during PID 3 to 7 (group 10), PID 8 to 12 (group 11), and PID 13 to 17 (group 12). Salinomycin therapy in group 2 calves resulted in substantial reductions in oocyst excretions and clinical signs.     

Dynamics of Eimeria oocyst excretion in dairy calves in the Province of Buenos Aires (Argentina), during their first 2 months of age

Clinical coccidiosis is associated with high fecal contamination and stress situations, mainly in animals under 1 year of age. Artificially fed dairy calves are one of the categories most prone to suffer from this parasitic disease. The study was carried out in a commercial dairy farm. Feces samples of heifer calves between 2 and 8 weeks old were taken monthly for oocyst counts and Eimeria spp. identification. Of the 862 feces samples analyzed, 48% presented oocysts. When grouping the results of monthly samplings of each age group, it was observed that this percentage increased in the group of calves between 20 and 40 days of life, reaching the peak average of 85% of infection prevalence in the group with between 26 and 30 days of age. The discharge of oocysts observed between 21 and 35 days of age was superior to the rest (p<0.05). This trend appeared every month throughout the whole year. However, during March, April, June, September and November, the curves in the group categories were higher than in the remaining months (p<0.05). Twelve Eimeria species were identified, being E. ellipsoidalis, E. bovis, E. zuernii and E. auburnensis those in highest numbers. E. ellipsoidalis had an important predominance in the opg composition, >75% up to 25 days of life (p<0.05). E. bovis reached peak values in the 26 and 30 days group (p<0.05), remaining without significant variations in the last stage of the artificial milk feeding period (approximately 60 days of life), when the oocyst counts were significantly low. Oocysts of E. auburnensis appeared in great proportion (46%) in the cultures later than the previous species (p<0.05), in calves of the age groups of between 46 and 50 days of age. Oocysts of E. zuernii showed no trend associated with age. The highest prevalence of infection and of oocyst values appeared during the periods with better environmental conditions for sporulation, survival and dispersion of oocysts (spring and autumn), coincident with the highest birth rates and an elevated number of calves in the paddock. Calves developed a process of natural "vaccination" against coccidiosis. This was demonstrated by the decrease in the quantity of animals shedding oocysts and in the number of oocysts eliminated at the end of the artificial milk feeding period.     

Effects of inoculations with Eimeria zuernii on young calves treated with decoquinate or narasin with or without dexamethasone

Sixteen 7-week-old Holstein male calves were inoculated with sporulated oocysts of Eimeria zuernii. Four calves (controls) were euthanatized and necropsied at 14 and 20 days after inoculation (DAI). Two calves were treated with 20 mg of dexamethasone (IM) on 13, 14, and 15 DAI and euthanatized and necropsied 17 DAI and 2 calves were given similar treatments and necropsied 20 DAI. The 8 other calves were euthanatized and necropsied 20 DAI. Two were started on the anticoccidial drug decoquinate in feed 13 DAI; 2 others were given decoquinate on the same schedule plus dexamethasone on 13,14, and 15 DAI. Two calves were given the antibiotic narasin in feed beginning 13 DAI and 2 calves were given parasin on the same schedule plus dexamethasone on 13,14, and 15 DAI. All calves, except 2 controls necropsied 14 DAI and 4 calves given decoquinate, discharged moderate-to-large numbers of oocysts in feces and had moderate-to-serve changes in fecal consistency. Histologic examinations revealed large numbers of endogenous stages in tissues of calves treated or not treated with dexamethasone. Few endogenous stages were observed in tissues from calves that were given decoquinate or decoquinate plus dexamethasone. Calves given narasin or narasin plus dexamethasone had moderate-to-large numbers of endogenous stages in the tissues.     

Infectivity of Cryptosporidium sp isolated from wild mice for calves and mice

A study was conducted to determine the incidence of cryptosporidiosis in wild mice (Mus musculus) and the infectivity of oocysts from their feces for susceptible calves. The presence of oocysts and the duration of shedding of oocysts in the feces were evaluated in 115 wild mice. Approximately 30% of the mice shed Cryptosporidium sp oocysts, without evidence of clinical infection; recurrence of oocyst shedding was found in about 50% of the mice. Oocysts from the feces of naturally infected mice were infective for calves and mice. Calves began shedding oocysts at 7 days and shed oocysts for about 10 days. Nonfatal, clinical cryptosporidiosis developed in 7 infected calves. The mice began shedding oocysts at 6 days and shed oocysts for 12 days. Fatalities or clinical infection did not develop in 5 infected mice. The results indicated that Cryptosporidium-infected wild mice may be a source of cryptosporidiosis in susceptible calves.     

Comparative therapeutic effect of toltrazuril, sulphadimidine and amprolium on Eimeria bovis and Eimeria zuernii given at different times following infection in buffalo calves (Bubalus bubalis)

We compared the therapeutic effect of three anticoccidial drugs (toltrazuril, sulphadimidine and amprolium) in buffalo (Bubalus bubalis) calves experimentally infected with Eimeria bovis (E. bovis) and E. zuernii oocysts (3 x 104oocyst/calf). Buffalo calves (1.5-4 month old, 70-kg body weight) were randomly allocated into 3 groups (9 calves each). Group T was experimentally infected with oocysts and treated with toltrazuril (20 mg/kg BW twice orally at a 1-week interval). Group S was experimentally infected with oocysts and treated with sulphadimidine (125 mg/kg injected IM followed by half dose for 4 successive days). Group A was experimentally infected with oocysts and treated with amprolium (50 mg/kg orally for 7 successive days). Each group had three subgroups (three calves/subgroup) to represent timing of the drug administration: 1st day of coccidia infection (FD), onset of clinical signs of coccidiosis (CC), and onset of oocyst shedding into the faeces (OS). Clinical signs, body-weight gain (BWG) and number of oocysts per gram feces (OPG) were monitored daily for 35 days post-infection (DPI). The OPG were reduced (but the BWG was not different) in the T calves compared to S and A calves. Within the same group, treatment from the 1st day of infection reduced the OPG and increased the BWG compared to the later treatment timings.     

Bovine coccidiosis: protective effects of low-level infection and coccidiostat treatments in calves

Twenty coccidia-free Holstein bull calves were allotted to groups to study effects of treatment with lasalocid and decoquinate on subsequent resistance to coccidiosis (Eimeria spp infections). Calves fed medicated rations of either drug at dosages of 50 mg/kg of feed (approx 1.2 mg/kg of body weight) had significantly fewer oocysts (P less than 0.01) than did nontreated controls regardless of other procedures used. Treated calves premunized with 2,000 oocysts/day for 5 days and later challenge inoculated with 200,000 oocysts did not develop diarrhea, unless the drugs were withdrawn from feed. Animals premunized (2,000 oocysts/day for 5 days) in absence of drug were no more resistant to the challenge inoculation than nonpremunized animals. These results indicated that lasalocid and decoquinate were efficacious coccidiostats and protected calves as long as they were administered. Cessation of drug treatment usually resulted in appearance of oocysts in feces and diarrhea. Premunization alone cannot be expected to prevent coccidiosis when animals are exposed to large numbers of oocysts.     

Effects of lasalocid on coccidial infection and growth in young dairy calves.

Effects of lasalocid on coccidial infection and on calf growth were examined in 16 Holstein bull calves. Calves were assigned randomly to a 2 x 2 factorial arrangement of starter ration containing 0 or 40 mg of lasalocid/kg of starter, beginning when calves were 3 days old (SE = 0.046), and single oral inoculation with 0 or 30,000 sporulated oocysts (Eimeria bovis) at 28 days. Pelleted calf starter was fed ad libitum from day 1; milk replacer was fed at a rate of 3.6 kg/d until day 28. Mean daily gain, dry-matter intake, and body weight were increased in calves fed lasalocid and decreased in those inoculated with coccidia. Addition of lasalocid to the feed improved gains by 8% in uninoculated calves and by 50% in inoculated calves. Fecal oocyst numbers were reduced when lasalocid was fed to inoculated calves. Feces were more abnormal in calves inoculated with coccidia. Respiration rates, rectal temperatures, PCV, and serum sodium and potassium concentrations were unaffected by treatment. On the basis of findings in this study, lasalocid minimized effects of coccidial challenge inoculation and increased growth of calves.     

Experimental bovine coccidiosis: control with monensin

Young Holstein-Friesian bull calves were used in a controlled experiment to evaluate the efficacy of monensin against coccidiosis. The calves were given oocysts of Eimeria bovis and/or E. zurnii. Medication was started 3 days prior to inoculation and continued during the 30-day experimental period. Oocyst shedding was quantified prior to and throughout the experiment and demonstrated that monensin at the rate of 20 or 30 g ton-1 of feed significantly reduced oocyst shedding and clinical coccidiosis. Clinical infection with E. zurnii was very difficult to establish, even when calves were treated with 20 mg dexamethasone IM on Days 12, 15, and 16 post-inoculation.     

Concurrent experimentally induced infection with Eimeria bovis and coronavirus in unweaned dairy calves.

Over a period of 3 summers, 21 colostrum-fed Holstein bull calves, 1 to 3 days old, were assigned to 7 replicates, each consisting of 3 calves. Within each replicate of 3 calves, 2 were selected at random, to be given 100,000 to 146,000 sporulated coccidia oocysts (principally Eimeria bovis) orally 60 hours after arrival at the college research farm. On the thirteenth day after coccidia inoculation, 1 of the 2 calves that had been given coccidia and the third calf that had not been inoculated, were given coronavirus by intranasal and oral routes. Calves were observed daily, and consistency of feces was scored visually. Nasal swab specimens for indirect immunofluorescent antibody testing for coronavirus and fecal samples for oocyst determination were obtained approximately every third day. Of 7 calves that were given only coronavirus, 3 developed diarrhea of short duration. Of 7 calves that were given only coccidia oocysts, 6 developed diarrhea. All 7 calves inoculated initially with coccidia and subsequently with coronavirus developed diarrhea. For 5 of 7 replicates, calves that were given coccidia and coronavirus developed diarrhea first. When overall severity, measured by fecal score and by blood in the feces, was compared, calves inoculated with coccidia followed by coronavirus were more severely affected (P less than 0.05) than were calves that were given only coronavirus. Calves that were given only coccidia oocysts appeared more severely affected than calves that were given only coronavirus, but differences were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of a metaphylactic treatment with diclazuril (Vecoxan) on the oocyst excretion and growth performance of calves exposed to a natural Eimeria infection

A multicenter field efficacy study was performed in six farms located in Belgium, France and Germany with a history of suspected coccidiosis outbreaks and the proven presence of Eimeria bovis and/or Eimeria zuernii. At each of these trial sites the calves were randomly allocated to two groups (T, treated; C, control) of similar size. In total, 231 calves were included in the study. Group T calves (n=116) were drenched with a single dose of diclazuril (Vecoxan, 1mg/kg body weight) close to the time of expected outbreak of coccidiosis (day 1 of the study period), group C calves (n=115) served as placebo-treated controls. Although E. bovis and/or E. zuernii were identified at all trial sites, clinical coccidiosis was only noted in 16% of the group C calves. At day 5 of the study period (4 days after treatment), faecal oocyst counts (opg, oocysts per gram) were substantially lower in group T ("short-term effect") compared to group C. At four trial sites, the respective values of groups T and C were significantly different (P=0.0132 to P=0.0001) in favour of group T. For the pooled data of all trial sites, this effect was highly significant (P<0.0001). The overall faecal oocyst counts from day 3 until day 21 of the study period ("Area Under the Curve") was significantly reduced in group T by 87.2-99.5% ("long-term effect") at five trial sites (P=0.0139 to P<0.0001). The pooled data revealed a highly significant effect of treatment on oocyst excretion over the observation period (P<0.0001). On five of the six trial sites, the average weight gain was higher in group T than in group C. On those trial sites, the average weight gain of group T calves exceeded that of the controls by 95-268g/day and by 2.0-6.0kg over the study period. This effect was statistically significant (P<0.01) at one trial site. Altogether the calves of group T gained on average 129g more weight daily than the controls (+2.7kg over the study period). For these pooled data, statistical analysis confirmed the positive effect of treatment of calves exposed to coccidiosis on growth performance (P=0.003). In conclusion, metaphylactic treatment with diclazuril efficiently controls coccidiosis in calves thus reducing environmental contamination with oocysts and preventing negative effects of natural exposure to coccidiosis on growth performance of calves.     

Number of Cryptosporidium parvum oocysts or Giardia spp cysts shed by dairy calves after natural infection

OBJECTIVE: To determine the total number of Cryptosporidium parvum oocysts and Giardia spp cysts shed by dairy calves during the period when they are most at risk after natural infection. ANIMALS: 478 calves naturally infected with C. parvum and 1,016 calves naturally infected with Giardia spp. PROCEDURE: Oocysts or cysts were enumerated from fecal specimens. Distribution of number of oocysts or cysts versus age was used to determine the best fitting mathematic function. Number of oocysts or cysts per gram of feces for a given duration of shedding was computed by determining the area under the curve. Total number of oocysts or cysts was calculated by taking the product of the resultant and the expected mass of feces. Results: Intensity of Cparvum oocyst shedding was best described by a second-order polynomial function. Shedding increased from 4 days of age, peaked at day 12, and then decreased. An infected 6-day-old calf would produce 3.89 x 10(10) oocysts until 12 days old. Pattern of shedding of Giardia spp cysts was best described by exponential functions. Intensity of shedding increased from 4 days of age, peaked at day 14, and then decreased. An infected calf would produce 3.8 x 10(7) cysts from day 50 until day 56. CONCLUSIONS AND CLINICAL RELEVANCE: The large number of oocysts and cysts shed indicates that shedding by dairy cattle poses a risk for susceptible calves and people. Estimates reported here may be useful to aid in designing cost-effective strategies to manage this risk.     

Occurrence and diversity of bovine coccidia at three localities in South Africa.

Information on the occurrence and diversity of coccidia infecting cattle in different farming systems in South Africa is lacking. The objective of the study was to determine the levels of infection of coccidia in cattle at three localities and to determine the Eimeria species occurring at each locality. Faecal samples (n=1936) were collected over a 13-month period from a dairy farm (Mallesons), a Bonsmara breeding farm (Kaalplaas) and a Nguni stud farm (Pienaars River). Samples were collected from adults >24 months old and calves <12 months old. The modified McMaster technique was used to determine OPG (oocysts per gram) of faeces. Samples with OPGs > or =2000 were allowed to sporulate in potassium dichromate solution at room temperature. Species identification was done by measurement and morphological characteristic of each species. At Mallesons, 29% of samples were positive, at Kaalplaas 50% and at Pienaars River 52%. The most prevalent species were Eimeria zuernii and E. ellipsoidalis at Mallesons, E. zuernii and E. bovis at Kaalplaas and E. bovis and E. zuernii at Pienaars River, respectively. Adults had very low OPGs. There was a pattern at the three localities in that high OPGs were only recorded in calves, which were also shedding the most pathogenic species.     

The prepatent and patent periods of Eimeria alabamensis and further description of the exogenous stages

Eimeria alabamensis infections were established in calves 5 to 6 weeks of age by adminestering 10 million, 80 million, or 100 million sporulated oocysts. The prepatent period was 6 to 8 days (mean 6.6). Oocyst discharges usually lasted for 2 to 3 days although a few calves passed oocysts throughout the rest of the 3-week observation period. Calves with oocyst discharge exceeding 1 million oocysts per g of feces had a moderate diarrhea at the time of peak oocyst discharge. No other clinical signs were observed in any of the infected calves. Reinoculations with 100 million sporulated oocysts given 3 weeks after the initial inoculations of 10 million or 80 million oocysts resulted in infections characterized by greatly reduced oocyst discharges. Sporulated oocysts of E. alabamensis were 16 to 24 μ by 12 to 16 μ and were usually ovoid. The oocyst wals consisted of two layers. Sporocysts were elongate-ellipsoid, had a distinct Stieda body, and were 10 to 12 μ by 4 to 6 μ. Completely sporulated oocysts were first observed after 5 days at 25 °C, and most were sporulated after 8 days. Oocysts did not sporulate at 4 °C, 33 °C, and 37 °C.     

Prevalence of Cryptosporidium parvum infection and pattern of oocyst shedding in calves in Japan

Cryptosporidium parvum infection and the pattern of oocyst shedding were observed in calves. A total of 480 fecal samples were collected from 30 calves (age, < or =30 days) over a period of 10 months from June 1998 to March 1999. A sucrose centrifugal flotation technique revealed 28/30 (93%) calves were passing Cryptosporidium oocysts. Oocyst shedding was first detected on the sixth day after birth, with 8% of the calves testing positive. This rate increased day by day and reached approximately 80% by day 15. Oocyst shedding varied from 1 to 13 days, with a mean of 7 days. Calves infected with C. parvum had a significantly higher rate of diarrhea (33%) than non-infected calves (8%) (P<0.05), suggesting C. parvum infection as the likely cause. The mean number of oocysts excreted by calves < or =30 days old was approximately 6x10(7) per gram of feces. These results indicated that one calf would excrete some 6x10(11) oocysts in the first month after birth, taking both the quantity of feces in a day and the period of excretion into consideration. Accordingly, it is clear that calves are important in the spread of cryptosporidiosis to calves and humans.     

Studies on the stage of action of lasalocid against Eimeria tenella and Eimeria acervulina in the chicken

Broiler chickens in battery pens were either fed a diet containing 100 ppm lasalocid or no drug for 24 h prior to inoculation with sporulated oocysts of Eimeria tenella or Eimeria acervulina. Different groups of birds remained on medicated feed for 24, 48, 72, 96, 120 or 144 h after inoculation. Conversely, other groups started on an unmedicated diet, were given medicated feed at different times after oocyst inoculation. Starting lasalocid medication 24 h (E. tenella) or 48 h (E. acervulina) after inoculation reduced the lesions and improved the weight gain. There was no significant difference in performance of birds after withdrawal of the drug at 48 h (E. tenella) or 72 h (E. acervulina) and thereafter. Starting lasalocid medication at 96 or 120 h did not suppress but rather reduced oocyst production.