Macrocyclic lactone-resistant Parascaris equorum on stud farms in Canada and effectiveness of fenbendazole and pyrantel pamoate

The aims of studies in 2002 and 2003 on three farms with 76 foals naturally infected with Parascaris equorum were to (i) identify if the nematode was resistant to ivermectin and moxidectin, and (ii) confirm the effectiveness of fenbendazole and pyrantel pamoate for the parasite. Twelve clinical trials, each with a Fecal Egg Count Reduction Test, were conducted on two Thoroughbred and one Standardbred farms in southwestern Ontario, Canada. In each trial, Parascaris eggs/g feces were estimated for each foal pre- and post-treatment using the Cornell-Wisconsin double flotation and Cornell-McMaster dilution techniques. On each farm and for each trial, foals were randomized into treatment groups. Treatments were ivermectin, moxidectin, fenbendazole, pyrantel pamoate administered at the manufacturers' recommended dosages, and some foals were untreated. The overall efficacy for ivermectin was 33.5% (19 foals) and for moxidectin 47.2% (28 foals). Fenbendazole (16 foals) and pyrantel pamoate (21 foals) were highly effective for P. equorum each at 97.6%. For fenbendazole, 15 foals had 100% and for pyrantel pamoate 17 foals had >97% with 14 at 100%.     

Parascaris equorum in foals and in their environment on a Swedish stud farm, with notes on treatment failure of ivermectin

Environmental contamination and the egg excretion pattern of the ascarid Parascaris equorum (Nematoda) was investigated in relation to anthelmintic treatment on a Swedish stud farm. Faecal samples from 15 foals, dewormed every 8th-week with a paste formulation of ivermectin at the standard dose rate of 0.2 mg/kg bodyweight, were collected at five sampling occasions between August and November 2006. In addition, soil samples were obtained from four paddocks used by these foals in November 2006. The number of eggs per gram (epg) was counted in both faeces and soil. Egg excretion started when the foals were 3-4 months, and reached the highest levels when they were approximately 5-month-old, and was then followed by a decline. Egg excretion seemed to be unaffected by ivermectin despite these foals were dewormed at regular intervals. In four out of five foals examined 10 days after treatment, epg actually increased. In contrast, when either fenbendazol or pyrantel embonate were used instead of ivermectin, treatments were effective. The number of eggs in soil was significantly higher in the permanent paddock compared to in the temporarily used soil paddock and in the summer paddocks.     

Impaired efficacy of ivermectin against Parascaris equorum, and both ivermectin and pyrantel against strongyle infections in trotter foals in Finland

In order to assess the resistance situation against macrocyclic lactones in Parascaris equorum and against tetrahydropyrimidine derivatives in strongyles in Finnish trotter horses, 112 foals on 18 farms, mostly 1 year old, were examined for these parasites with a modified McMaster faecal flotation method. P. equorum positive foals (n=24) were given ivermectin orally at a dose of 200 μg/kg b.w., while strongyle positive but P. equorum negative foals (n=38) received pyrantel embonate orally at a dose of 19 mg/kg. Sixteen P. equorum infected foals, treated with ivermectin, also harboured strongyles. During the anthelmintic treatment visit to the farm, Faecal Egg Count Reduction Test (FECRT) reference (first) samples were collected. Fourteen days later, the second sampling (reduction samples) was done. The FECR was calculated for each foal/parasite combination. The reduction efficacies of ivermectin against P. equorum (mean 52%, calculated from the individual egg count reductions) and pyrantel against strongyles (43%) were strongly indicative of widespread resistance. Also indication of ivermectin resistance among strongyles was seen. The widespread use of anthelmintics for Finnish horses obviously has resulted in resistance, as has happened elsewhere, too.     

Determining Treatment to Control Two Multidrug-Resistant Parasites on a Texas Horse Farm

A study was undertaken at the Texas A&M Horse Center to evaluate and compare the effectiveness of three anthelmintics—ivermectin, fenbendazole, and a combination of ivermectin and pyrantel pamoate—on fecal egg count reductions of cyathostomes and Parascaris equorum in 30 naturally infected foals. The foals were randomized into three treatment groups, with individuals being rerandomized after each 8-week observation period. The treatments of ivermectin and fenbendazole were given at the manufacturer's recommended doses, and the pyrantel treatment was given at two times the manufacturer's recommended dose. Fecal egg counts were performed at the time of treatment and at 2-week intervals after treatment for a total of 8 weeks. Each foal received a total of three treatments during the course of the study. Fecal egg counts were performed by a modified McMaster's test, with a sensitivity of 25 eggs per gram of feces, and by the modified Wisconsin double centrifugal flotation technique, with a sensitivity of 0.2 eggs per gram of feces. Fecal egg reduction percentages were calculated. Analysis of the results showed that ivermectin, either used alone or with pyrantel, was a more effective anthelmintic for cyathostome (small strongyle) control than fenbendazole. Fenbendazole and pyrantel showed a higher initial reduction in Parascaris egg counts when compared with the ivermectin-only-treated group, but this difference lessened over time. The use of the combination treatment showed the best results for controlling both parasites, indicating that a combination of anthelmintics may be necessary to control parasites on some equine farms.     

A Field Study on the Effect of Some Anthelmintics on Cyathostomins of Horses in Sweden

The objective of the study was to investigate different aspects on the efficacy of three anthelmintics on cyathostomin nematodes of Swedish horses. A faecal egg count reduction (FECR) test was performed on 26 farms. Horses were treated orally with recommended doses of ivermectin, pyrantel pamoate or fenbendazole. Faecal samples were collected on the day of deworming and 7, 14 and 21 days later. No resistance was shown against ivermectin; the FECR was constantly >99%. The effect of pyrantel was assessed as equivocal in 6 farms 14 days after treatment; the mean FECR was 99%. As many as 72% of the fenbendazole-treated groups met the criteria for resistance; the mean FECR was 86%, ranging from 56% to 100%. A re-investigation of two farms where pyrantel resistance had been suspected clearly revealed unsatisfactory efficacy of pyrantel on one of these farms; the FECR varied from 72% to 89%. Twenty-six of the horses previously dosed with pyrantel or fenbendazole, and which still excreted ≥150 eggs per gram of faeces 14 days after treatment, were dewormed with ivermectin and fenbendazole or pyrantel in order to eliminate the remaining cyathostomins. A total of 13 cyathostomin species were identified from horses that initially received fenbendazole and seven species were identified from pyrantel-treated individuals. The egg reappearance period (ERP) following treatment with ivermectin and pyrantel was investigated on two farms. The shortest ERP after ivermectin treatment was 8 weeks and after pyrantel was 5 weeks. We conclude that no substantial reversion to benzimidazole susceptibility had taken place, although these drugs have scarcely been used (<5%) in horses for the last 10 years. Pyrantel-resistant populations of cyathostomins are present on Swedish horse farms, but the overall efficacy of pyrantel is still acceptable.     

Identification of foals infected with Parascaris equorum apparently resistant to ivermectin

During September 2002, routine fecal examinations performed on 16 Thoroughbred foals residing on a farm outside Toronto, Ontario, Canada, revealed low to moderate numbers of Parascaris equorum eggs in feces from 9 of the 16. All foals were then treated with ivermectin at a dose of 220 to 280 microg/kg (100 to 127 microg/lb), p.o., and fecal egg counts were repeated 12 days later. Fecal P. equorum egg counts increased between the first and second fecal examination in 7 foals, were unchanged in 1, and decreased in 5. Fecal samples were collected 13 days after treatment from 21 additional foals that had been treated with ivermectin at the same dose, and P. equorum eggs were detected in 12 of the 21. For all 37 foals, high P. equorum egg counts (> or = 100 eggs/g of feces) 12 to 13 days after ivermectin treatment were significantly more likely in foals that had been regularly treated with ivermectin since birth and permanently resided on the farm, compared with foals that had been treated with other anthelmintics or had an unknown deworming history. Collectively, these data suggested that P. equorum in these foals was resistant to ivermectin administered at the recommended dose.     

Management of drug-resistant cyathostominosis on a breeding farm in central North Carolina

REASONS FOR PERFORMING STUDY: Possible anthelmintic resistance on a breeding farm where a rapid rotation anthelmintic programme had been implemented for 9 years was investigated. Cyathostomins resistant to fenbendazole and pyrantel were documented by faecal worm egg count reduction test (FWECRT). OBJECTIVES: To 1) manage small strongyle transmission in a herd of horses in which resistance to both pyrantel pamoate and fenbendazole was identified and thereby reduce the risk of clinical disease in the individual animal, 2) monitor the change in resistance patterns over time and 3) monitor the efficacy of ivermectin over the study period. METHODS: Targeted ivermectin treatment of horses on the farm was instituted for mature horses with faecal worm egg counts (FWEC) > 200 eggs/g (epg) and for horses < age 2 years with FWEC > 100 epg. RESULTS: Over a 30 month period, targeted ivermectin treatment achieved acceptable control in mares, as judged by FWEC, and improved control of patent cyathostome infection in consecutive foal crops. Egg reappearance time (ERT) after treatment with ivermectin was < 8 weeks in mares and foals more frequently in the second year of the study than in the first year. Numbers of anthelmintic treatments were reduced by 77.6 and 533% in the mare and foal group, respectively. CONCLUSIONS: Targeted ivermectin treatment may be an economically viable method of managing multiple drug resistant cyathostominosis. POTENTIAL RELEVANCE: Use of ivermectin should be monitored closely for development of resistance.     

Comparison of the efficacy of ivermectin, oxibendazole, and pyrantel pamoate against 28-day Parascaris equorum larvae in the intestine of pony foals

Sixteen helminth-free pony foals were inoculated with a mean (+/- SD) 2,000 (+/- 545.5) infective Parascaris equorum eggs (day 0). Foals were allocated to replicates of 4, and treatments within each replicate were assigned at random. Treatment administered on postinoculation day (PID) 28 included no treatment (control), 0.2 mg of ivermectin/kg of body weight, 10 mg of oxibendazole/kg, or 6.6 mg of pyrantel base (pamoate)/kg. Paste formulations of the anthelmintics were administered orally. The foals were euthanatized 14 days after treatment (PID 42) and examined for P equorum larvae in the small intestine. The mean +/- SD (and range) numbers of fourth-stage P equorum larvae recovered from nontreated foals and those treated with ivermectin, pyrantel, or oxibendazole were 1,603.8 +/- 1,026.8 (305 to 2,480), 29.3 +/- 55.8 (0 to 113), 413.0 +/- 568.1 (0 to 1,204), or 889.5 +/- 1,123.1 (1 to 2,345), respectively. Compared with the value for control (nontreated) foals, treatment with ivermectin, pyrantel, and oxibendazole was 98.2, 74.2, and 44.5% effective, respectively, when administered 28 days after experimentally induced infection with P equorum. Adverse reactions attributable to treatment were not observed.     

Critical tests and clinical trials on oxibendazole in horses with special reference to removal of Parascaris equorum.

The efficacy of oxibendazole given at dose level of 10 mg/kg of body weight was determined by 10 critical tests in foals and by 2 clinical trials in 20 foals (16 treated, 4 nontreated), with special interest in the drug activity against Parascaris equorum. The drug was uniformly efficacious (100%) against P equorum in the 10 critical-test foals, each having between 22 and 236 ascarids. Posttreatment reductions of ascarid egg counts in fecal samples were also 100% in suckling foals treated with oxibendazole given as a drench. Ascarid eggs did not reappear in fecal samples until the 8th week after foals were treated. A paste formulation of oxibendazole at 10 mg/kg also eliminated ascarid eggs from feces of 12 suckling foals. Strongyle EPG were markedly reduced by oxibendazole in the 10 critical-test foals and in 16 treated sucklings in the clinical trials. Egg and larval count data on foals in both the critical tests and the clinical trials also indicated oxibendazole was active against Strongyloides westeri. Untoward effects of treatment with oxibendazole were not observed.     

Evidence of host adaptation in Lawsonia intracellularis infections

Background

Lawsonia intracellularis is the causative agent of proliferative enteropathy, an endemic disease in pigs and an emerging concern in horses. Enterocyte hyperplasia is a common lesion in every case but there are differences regarding clinical and pathological presentations among affected species. We hypothesize that host susceptibility to L. intracellularis infection depends on the species of origin of the bacterial isolate. The objective of this study was to evaluate the susceptibilities of pigs and horses to L. intracellularis infection using either a porcine or an equine isolate.

Materials and methods

Twelve foals and eighteen pigs were equally divided into three groups and infected with either a porcine or an equine isolate (10⁹L. Intracellularis/challenged animal), and a saline solution (negative control group). The animals were monitored regarding clinical signs, average of daily weight gain, fecal shedding of the bacteria by PCR and humoral serological response.

Results

Foals infected with the equine isolate developed moderate to severe clinical signs and maintained a lower average of weight gain compared to control foals. Fecal quantitative PCR in equine isolate-infected foals revealed higher amounts of bacterial DNA associated with longer duration of shedding compared with porcine isolate-infected foals. All four foals infected with the equine isolate demonstrated higher IgG titers in the serum compared with porcine isolate-infected foals. In the pig trial, diarrhea and seroconversion were only observed in animals infected with the porcine isolate. Pathological changes typical of proliferative enteropathy were observed in the necropsied foal infected with equine isolate and in the two necropsied pigs infected with the porcine isolate.

Conclusions

Evident clinical signs, longer periods of bacterial shedding and stronger serologic immune responses were observed in animals infected with species-specific isolates. These results show that host susceptibility is driven by the origin of the isolated L. intracellularis strain.     

Acute small intestinal obstruction associated with Parascaris equorum infection in young horses: 25 cases (1985-2004)

AIMS: To retrospectively evaluate the medical and surgical records of horses with acute small intestinal obstructions associated with Parascaris equorum infection; to describe the gastrointestinal lesions; and to determine the outcome of cases with such lesions. METHODS: Records of 25 horses with acute small intestinal obstruction associated with P. equorum between 1985 and 2004 were reviewed to determine signalment, history, physical examination, surgical or post-mortem findings, and outcome. RESULTS: All horses except one were less than 12 months old. Standardbreds were over-represented in the population studied. Sixteen horses (72%) had been administered anthelmintics, including pyrantel (n=8), ivermectin (n=7), and trichlorphon (n=1), within 24 h prior to the onset of colic. Of the 25 cases reviewed, 16 had simple obstructive ascarid impactions (SOAIs), and nine had complicated obstructive ascarid impaction (COAI) including volvulus (n=6) or intussusception (n=3), both concurrent with ascarid impaction of the small intestine. Short-term survival (discharge from hospital) occurred in 79% of horses treated for SOAI, and was 64% for all horses. Long-term survival (>1 year) occurred in 33% of horses with SOAI, and the overall long-term survival was 27% for all horses. Formation of adhesions was the most frequent finding associated with death for horses that did not survive long-term. CONCLUSIONS AND CLINICAL RELEVANCE: The incidence of anthelmintic treatment within 24 h of the onset of colic in this study population (72%) was higher than that previously reported. Resistance of P. equorum to ivermectin recently reported in Ontario may be associated with increased ascarid burdens, predisposing horses to ascarid impaction. The long-term survival of these horses was better than that reported previously.     

Efficacy of ivermectin in the treatment of induced Parascaris equorum infection in pony foals

Eighteen pony foals inoculated with 1,500 +/- 109 infective Parascaris equorum eggs were given 0.02 ml of ivermectin vehicle (liquid)/kg of body weight, PO, (control); 0.2 mg of ivermectin paste/kg, PO; or 0.2 mg ivermectin liquid/kg, PO, on postinoculation day (PID) 28. Foals were euthanatized on PID 42, and the small intestinal contents were examined for P equorum larvae. The mean number of fourth-stage P equorum larvae in foals treated with ivermectin paste and liquid were 3.5 and 6, respectively. Significantly (P less than 0.01) higher mean numbers of larvae (1,250) were detected in foals treated with ivermectin vehicle. Larvae recovered from foals treated with ivermectin vehicle were of significantly (P less than 0.002) longer mean length than those from foals treated with ivermectin paste or liquid. Gross examination of lungs and liver revealed similar pathologic changes from the migration of P equorum in all foals. Adverse reaction to treatment was not observed.     

Evidence of Ivermectin Resistance by Parascaris equorum on a Texas Horse Farm

By collecting fecal samples every 2 weeks beginning at 2 months of age, 32 foals from a single Texas farm were monitored. The foals were administered ivermectin paste at the time of the first collection and again monthly. When foals had Parascaris egg counts higher 2 weeks after ivermectin treatment than at treatment, they were administered pyrantel pamoate at the manufacturer's recommended dose (6.6 mg/kg) or at twice the recommended dose (13.2 mg/ kg) when tapeworm eggs were also detected. An elevation or only minimal reduction (less than 75%) in Parascaris egg counts was seen 2 weeks after ivermectin treatment until the foals were 8 months of age, at which time there was an 85% reduction in fecal egg count after treatment. When pyrantel was administered at the manufacturer's recommended dose, a 42% to 84% reduction in egg counts occurred, but at 13.2 mg/kg there was a 98% to 100% reduction in fecal egg counts 2 weeks posttreatment. However, pyrantel failed to control strongylate egg counts even at the elevated dose, whereas ivermectin reduced strongylate fecal egg counts by greater than 99%, determined 2 weeks posttreatment. Pyrantel, but not ivermectin, lowered Parascaris egg counts. Ivermectin, but not pyrantel, lowered strongyle egg counts 2 weeks post administration. A single drug for all ages of horses approach to parasite control requires rethinking. Combinations of drugs or more careful evaluation of anthelmintics in foals may be necessary for continued parasite control.     

Plasma C‐Reactive Protein and Haptoglobin Concentrations in Critically Ill Neonatal Foals

Background

Accurate diagnostic markers for sepsis in neonatal foals are needed. Plasma C‐reactive protein concentration (p[CRP]) and haptoglobin concentration (p[Hp]) are well‐established biomarkers of infection in humans, but studies are lacking in foals.

Hypotheses

p[CRP]) and p[Hp] are increased in septic foals compared to sick nonseptic and healthy control foals, and are predictive of survival.

Animals

Eighty critically ill foals (40 septic, 40 sick nonseptic) and 39 healthy control foals <1 week of age.

Methods

Multicenter, prospective observational clinical study. Venous blood was collected at admission from septic and sick nonseptic foals and from clinically healthy foals at 24 h of age. A diagnosis of sepsis was made based on positive blood culture or a sepsis score >11, and p[CRP] and p[Hp] were measured by using ELISA tests. Data were analyzed by using the Mann‐Whitney U‐test and forward stepwise multivariable linear regression. P < .05 was considered significant.

Results

Plasma [CRP] was positively associated with age, serum globulin, adrenomedullin, and bilirubin concentrations, aspartate aminotransferase activity, glutamyl‐transferase activity, band neutrophil count, and rectal temperature, and was increased in foals with toxic neutrophils, enterocolitis, colic, rib fractures and septic arthritis. Surprisingly, p[Hp] was lower in septic foals than in sick nonseptic foals. Neither p[CRP] or p[Hp] was predictive of survival in critically ill foals.

Conclusions and Clinical Importance

Plasma [CRP] increases with inflammation in neonatal foals but is not indicative of sepsis. Single time point, admission sampling of p[CRP] and p[Hp] do not appear to be useful biomarkers for sepsis in foals.     

Brainstem Auditory Evoked Responses in Foals: Reference Values,Effect of Age,Rate of Acoustic Stimulation,and Neurologic Deficits

Background

Age and rate of acoustic stimulation affect peak latencies in brainstem auditory evoked responses (BAER) in humans. Those effects are unknown in foals.

Hypothesis/Objectives

Our goals were to (1) establish reference values for BAER in foals by using 3 different stimulation protocols, (2) evaluate the effects of age and stimulation frequencies on BAER tracing in foals up to 6 months old, and (3) compare the data with BAER obtained from foals with central nervous system (CNS) disorders.

Animals

Thirty‐nine neurologically normal foals and 16 foals with neurologic diseases.

Methods

Prospective observational clinical study. BAER recorded by using 3 protocols of stimulation (11.33 repetitions per second [Hz]/70 decibel normal hearing level [dBNHL]; 11.33 Hz/90 dBNHL; 90 Hz/70 dBNHL).

Results

No effect of age was observed in normal foals (P > .005). No significant difference was observed for latencies and interpeak latencies (IPL) when comparing foals with neurologic diseases and normal foals (P > .05), but 78.6% of foals with neurologic diseases had an asymmetry in their tracing, reflecting a difference in conduction time between the left and right side of the brainstem. Increasing the stimulation rate did not improve detection of CNS disorders.

Conclusions and Clinical Importance

We propose BAER reference values for foals up to 6 months of age by using 3 protocols. Most foals with neurologic deficits had abnormal BAER tracing.     

Expulsion of small strongyle nematodes (cyathostomin spp) following deworming of horses on a stud farm in Sweden

This study was conducted on a stud farm in Sweden to investigate the species composition of cyathostomins expelled in the faeces of horses after deworming using three different anthelmintic preparations. Twenty-seven horses excreting > or = 200 strongyle eggs per gram faeces (EPG) were divided into three comparable groups and dewormed on day 0 with either of following compounds: 0.2 mg ivermectin per kg body weight (bw), 19 mg pyrantel pamoate per kg bw or 7.5 mg fenbendazole per kg bw. For each of the 3 days following anthelmintic treatment faeces was collected from individual horses and subsamples were fixed in formalin. Four days after the anthelmintic treatment all horses were re-treated with ivermectin and faeces was collected on day 5. Individual subsamples from each of the four sampling occasions were examined for cyathostomin nematodes. Sixty-three to 270 worms per horse were identified to the species level. The majority of the worms recovered were expelled during the first day from horses treated with ivermectin or pyrantel pamoate, and during the second day from horses treated with fenbendazole. Fifteen cyathostomin species were identified and the six most prevalent were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicocyclus leptostomus, Cylicostephanus minutus and Cylicostephanus calicatus. These species composed 91% of the total burden of cyathostomins. The number of species found per horse ranged from 6 to 13, with an average of 9. No significant differences in species composition or distribution were found between the treatment groups. On day 5, i.e. 1 day after the last ivermectin treatment, 93% of the adult worms were recovered from horses in the fenbendazole group.This study showed that it was possible to identify cyathostomins expelled in faeces of dewormed horses, and that the most prevalent species corresponded to those found in autopsy surveys performed in other countries.     

Field efficacy of ivermectin, fenbendazole and pyrantel embonate paste anthelmintics in horses

Three anthelmintic pastes were compared in terms of their ability to suppress the output of parasite eggs in the faeces of 108 grazing horses at four sites in Britain; the horses were treated once with either ivermectin, fenbendazole or pyrantel. At each site, the horses grazed together throughout the trials which took place during the summers of 1985 and 1986. The median periods before parasite eggs reappeared in faeces were 70 days for ivermectin, 14 days for fenbendazole and 39 days for pyrantel embonate. Geometric mean faecal egg counts in the groups treated with ivermectin and pyrantel were significantly less (P less than 0.05) than in the fenbendazole group on days 21, 28, 35 and 42 after treatment. On days 49, 56, 63 and 70 the mean egg counts in the ivermectin group were significantly lower (P less than 0.05) than those in either of the other groups. The results indicated that in order to ensure minimal contamination of pastures, grazing horses treated with ivermectin paste would have required a second treatment approximately 10 weeks after the first, and to achieve similar control with fenbendazole or pyrantel embonate, a second treatment would have been required after approximately two weeks and six weeks, respectively.     

Gallium Maltolate as an Alternative to Macrolides for Treatment of Presumed Rhodococcus equi Pneumonia in Foals

Background

Macrolide‐resistant isolates of Rhodococcus equi are emerging, prompting the search for clinically effective alternative antimicrobials.

Hypothesis

The proportion of foals with ultrasonographic evidence of pneumonia presumed to be caused by R. equi that had a successful outcome when administered gallium maltolate (GaM) PO would not be more than 10% inferior (ie, lower) than that of foals receiving standard treatment.

Animals

Fifty‐four foals with subclinical pulmonary abscesses among 509 foals at 6 breeding farms in Kentucky.

Methods

Controlled, randomized, prospective noninferiority study. Foals with ultrasonographic lesions >1 cm in diameter (n = 54) were randomly allocated to receive per os either clarithromycin combined with rifampin (CLR+R) or GaM, and followed up for 28 days by daily physical inspections and weekly (n = 1 farm) or biweekly (n = 4 farms) thoracic ultrasound examinations by individuals unaware of treatment‐group assignments. Treatment success was defined as resolution of ultrasonographically identified pulmonary abscesses within 28 days of initiating treatment. Noninferiority was defined as a 90% confidence interval for the observed difference in CLR+R minus GaM that was ≤10%.

Results

The proportion of GaM‐treated foals that resolved (70%; 14/20) was similar to that of foals treated with CLR+R (74%; 25/34), but we failed to demonstrate noninferiority for GaM relative to CLR+R; however, GaM was noninferior to CLR+R treatment when results from a noncompliant farm were excluded.

Conclusions and Clinical Importance

Gallium maltolate is not inferior to macrolides for treating foals with subclinical pneumonia. Use of GaM might reduce pressure for macrolide‐resistance in R. equi.     

Efficacy of different treatment regimes against setariosis (Setaria tundra,Nematoda: Filarioidea) and associated peritonitis in reindeer

Background

When a severe peritonitis outbreak in semi-domesticated reindeer was noticed in 2003 in Finland, the concerned industry urged immediate preventive actions in order to avoid detrimental effects of S. tundra and further economical losses. A research programme was swiftly initiated to study S. tundra and its impact on the health and wellbeing of reindeer.

Methods

The ultimate aim of this study was to test the efficacy of different treatment regimes against S. tundra and associated peritonitis in reindeer. The timing of the trials was planned to be compatible with the annual rhythm of the reindeer management; (1) the treatment of calves in midsummer, during routine calf ear marking, with ivermectin injection prophylaxis and deltamethrin pour-on solution as a repellent against insect vectors, (2) the treatment of infected calves in early autumn with ivermectin injection, and (3) ivermectin treatment of breeding reindeer in winter. The results were assessed using the post mortem inspection data and S. tundra detection. Finally, to evaluate on the population level the influence of the annual (late autumn-winter) ivermectin treatment of breeding reindeer on the transmission dynamics of S. tundra, a questionnaire survey was conducted.

Results

In autumn, ivermectin treatment was efficient against peritonitis and in midsummer had a slight negative impact on the degree of peritonitis and positive on the fat layer, but deltamethrin had none. Ivermectin was efficient against adult S. tundra and its smf. All the reindeer herding cooperatives answered the questionnaire and it appeared that antiparasitic treatment of reindeer population was intense during the study period, when 64–90% of the animals were treated. In the southern part of the Finnish reindeer husbandry area, oral administration of ivermectin was commonly used.

Conclusion

Autumn, and to a lesser degree summer, treatment of reindeer calves with injectable ivermectin resulted in decreased severity of peritonitis and perihepatitis in reindeer calves due to setariosis. In the case of necessity for animal welfare reasons, treatment during early autumn round ups should be considered. On the population level, massive and routinely applied antiparasitic treatments can improve the health of breeding reindeer and decrease the mortality and the number of carriers but during the outbreak could not prevent its movement and expansion to the North.