Efficacy of sulfonamides and Baycox® against Isospora suis in experimental infections of suckling piglets

Abstract

Sulfonamide treatment of piglets against neonatal coccidiosis has frequently been suggested in the literature. In order to evaluate the efficacy of sulfonamides against experimental Isospora suis infections in suckling piglets (oral infection with 1,500 sporulated oocysts of I. suis per piglet on the fourth day of life), two trials were conducted. In trial I, oral sulfadimidine (group Sulfa-Oral) was applied in doses of 100 mg/kg of body weight (BW) 1 day before infection and 75 mg/kg BW daily for the following 5 days, and sulfamethoxypyrimidine (SMP) was applied parenterally in daily doses of 75 mg/kg BW for the same time period. In trial II, SMP was applied parenterally in doses of 75 mg/kg BW (a) from the day of infection daily for 7 days (SMP-Standard), (b) for 2 days starting on the day of infection (SMP-Early), (c) for 3 days starting 2 days post-infection (d.p.i.; SMP-Middle), (d) for 2 days starting 5 d.p.i. (SMP-Late), and (e) every other day from the day of infection until 6 d.p.i. (SMP-Alternating), as well as (f) orally in doses of 75 mg/kg BW from the day of infection for 7 days (SMP-Oral). The sulfonamide-treated groups were compared to a toltrazuril-treated group (single oral treatment with Baycox® 5% suspension, 20 mg/kg BW 2 d.p.i.) and to a water-treated Control group. Each group consisted of seven to nine piglets. The parameters evaluated were oocyst excretion and fecal consistency/diarrhea from 4 to 15 d.p.i. Sulfa-Oral, SMP-Early, and SMP-Late had no significant effect in reduction of oocyst excretion and diarrhea, whereas treatment for 3-7 days with SMP reduced both parasite shedding and diarrhea significantly. Oral treatment with SMP was comparable to parenteral application. Baycox® in a single application had the most pronounced effect and completely suppressed oocyst excretion and diarrhea during the examination period. It could be shown that repeated application of sulfonamides, provided that the appropriate time period after infection is covered, can in principle be used to control piglet coccidiosis; however, the amount of work required is considerable, and the practicability is poor. Due to the short half-life of sulfonamides in pigs and the lack of predictability of the time point of infection, an efficient application of sulfonamides to control piglet coccidiosis under field conditions appears unlikely. Baycox®, on the other hand, applied once during the prepatent period of infection, had a lasting effect and can be used to most effectively control I. suis.

Experimentally confirmed toltrazuril resistance in a field isolate of Cystoisospora suis

“…Before performing resistance studies the field isolate was passaged once through piglets for collection of fresh, viable oocysts. A toltrazuril-sensitive strain of C. suis, Wien-I [20], was used for comparison between the strains which was maintained and passaged regularly in suckling piglets for the production of infectious oocysts at the Institute of Parasitology, University of Veterinary Medicine Vienna, Austria. The strain is passaged every 3-6 months and infectivity in vivo and susceptibility to toltrazuril are assessed regularly.…”

“…Use of Baycox® in piglet coccidiosis was first authorized in Australia in 1998 to be administered once in the first week of life at a dose of 20 mg/kg body weight (BW) [19]. A single oral treatment with toltrazuril administered during the prepatent period provided effective and sustained suppression of oocyst shedding and diarrhea in piglets experimentally infected with C. suis [17,[20][21][22] and under field conditions [23][24][25][26][27][28]. However, emerging resistance in poultry coccidia against anticoccidials including toltrazuril is of growing concern [29][30][31].…”

Field Evaluation of the Effectiveness of an Oral Toltrazuril and Iron Combination (Baycox® Iron) in Maintaining Weaning Weight by Preventing Coccidiosis and Anaemia in Neonatal Piglets

“…For example, toltrazuril administered at a dose of 20 30 mg/kg to piglets at 3 days of age provided excellent prophylaxis against I. suis coccidiosis with significantly less diarrhoea and lower oocyst counts at approximately 12 and 21 days of age when compared to an untreated control group (Madsen et al 1994). A single oral treatment with toltrazuril administered during the pre-patent period provided effective and sustained suppression of oocyst shedding and diarrhoea in piglets experimentally infected with I. suis (Joachim and Mundt 2011). In an on-farm Venezuelan study (Boulanger et al 1994), where piglets were treated at 5 days of age with 20 mg/kg toltrazuril, treated piglets were heavier at weaning and had lower mortality than their untreated counterparts.…”

Isospora suis in an Epithelial Cell Culture System – An In Vitro Model for Sexual Development in Coccidia

“…This system provided complete development to oocysts but no sporulation [15]. Beside these findings in vivo infection models for neonatal porcine coccidiosis are well described [16,17] and successfully used for drug efficacy testing [18,19], investigations of the immune response [20–22], and for co-infection modeling [23]. Therefore, a reproducible in vitro system including sexual stages and sporulated oocysts together with the knowledge obtained during in vivo trials could deliver an integral approach to the understanding of neonatal porcine coccidiosis and coccidian development as well as host-parasite interactions in these parasites.…”