In 2010, a commercial 250 sow farrow to finish herd in Jutland, Denmark was reporting increased problems of diarrhea in weaners. The herd had excellent production records. The average daily gain was 596 g and mortality rate was 0.7% in the weaning facility. Feed conversion rate was not recorded. The antibiotic consumption per weaned pig was approximately 80% of the mean consumption for weaners (7–30 kg bodyweight) on Danish farms (mean = 8.4 animal daily doses per 15 kg pig produced (Danmap Citation2010)). Three different home-mixed dry feed diets were used in the weaning facility. All diets were traditional weaning diets based on wheat, barley, and toasted soybean meal, and specially designed for each age group. Every single batch of pigs had outbreaks of diarrhea where the farmer considered batch medication necessary. Especially the larger pigs with-in a batch experienced diarrhea. The outbreaks started approximately 2–3 weeks post weaning when feed diet number two was used and each batch of pigs had between two and three recurring episodes of diarrhea despite the use of therapeutic batch medication. Currently, treatment was performed using apramycin in water for 3–4 days. The recurring episodes of diarrhea occurred approximately 7 days after termination of each batch medication. Further, antibiotic injections with oxytetracycline for individual pigs with diarrhea were deemed necessary. Some pigs also got diarrhea again after termination of this individual treatment. Diarrhea was not reported to be a problem when feed diet number three was used the last 14 days before moving the pigs to the grow/finishing facility. In May and July 2010, the herd veterinarian had performed a laboratory investigation. Intestines from one pig had been examined for Brachyspira hyodysenteriea, Brachyspira pilosicoli and Salmonellae spp. by PCR. Fixated intestinal tissues obtained from another two pigs had been examined for Brachyspira spp. by in situ hybridization (ISH) and Lawsonia intracellularis and Porcine circovirus type 2 (PCV2) by immunohistochemistry (IHC). These laboratory diagnostic examinations were all negative.
In August 2010, the herd was visited during a typical first episode of acute diarrhea outbreak requiring treatment in a batch of weaned pigs. No animals were treated before the herd visit in order to obtain samples from non-medicated acute diseased animals. The weaning facility contained a total of 1040 pigs (260 pigs per room, 17 pigs per pen). The pigs were observed to be in a general good condition and no unthrifty pigs were observed in any of the rooms. Diarrhea status of the pigs was clinically assessed using a fecal consistency scale with four categories as previously described (Pedersen and Toft Citation2011). The diarrhea prevalence in the four batches of pigs was estimated as previously described (Pedersen et al. Citation2011). The diarrhea prevalence was low in pigs 1 week post weaning, approximately 30% in pigs 3 weeks post weaning, approximately 25% in pigs 5 weeks post weaning, and low in pigs 7 weeks post weaning. The feed was considered coarsely ground at examination compared to Danish recommendations for weaner diets. The diet compositions were within Danish recommendations in relation to the levels of amino acids, minerals, and other nutrients. The first diet contained a lower content of protein than diet number two. The primary protein source in diet number two was toasted soybean meal, which was not included in diet number one. Further, diet number two contained higher levels of wheat compared to barley than diet number one. The last diet in the weaner facility contained less protein and lower level of wheat compared to barley than diet number one and two.
Acute diseased diarrheic pigs were selected for euthanasia and necropsy. Tissues for fixation were collected within 5 min after euthanasia from jejunum, ileum, and colon. Histological examinations included Brachyspira spp. and Escherichia coli by fluorescent ISH, PCV2, and L. intracellularis by IHC and Haematoxylin–Eosin stain. Fecal samples were collected from the euthanized pigs and examined for PCV2, L. intracellularis, B. pilosicoli, and E. coli fimbriae type 4+18 (F4+F18) using quantitative real-time PCR (qPCR) and for parasitic eggs by McMaster. Blood samples were obtained from two pigs selected at convenience in every second pen in each room and examined for PCV2 and L. intracellularis specific antibodies. Fecal samples were collected by selecting the five most-watery fecal pools from the pen floor in each room. The fecal samples were examined for PCV2, L. intracellularis, B. pilosicoli, and E. coli F4+F18 using quantitative PCR and for parasitic eggs by McMaster.
All laboratory examinations, including gross pathology, were performed at The National Veterinary Institute, Danish Technical University. The ISH, IHC, qPCR, and serology procedures were performed as previously described (Boye et al. Citation1998; Boesen et al. Citation2005; Enoe et al. Citation2006; Jensen et al. Citation2006; Hjulsager et al. Citation2009; Stahl et al. Citation2011).
The results of the laboratory examinations are displayed in and . In the live pigs, 5 weeks post weaning two pigs had low levels of E. coli F18 in feces (<105 copies per gram feces). One of those pigs also had low levels of PCV2 in feces (>104 and <105 copies per gram feces). In the pigs 7 weeks post weaning one pig had moderate levels of PCV2 (>105 and <107 copies per gram feces) and three pigs had low levels of PCV2 in feces.
Table 1. Results of laboratory examinations of a cross-sectional sample of live pigs in a herd with outbreaks of diarrhea post weaning.
Table 2. Results of gross pathological, histopathological, and laboratory examinations for euthanized pigs with watery diarrhea.
All examined blood samples were PCV2 antibody positive with low titers indicating maternal antibodies. The titers ranged from 50 to 1250 in pigs 3 weeks post weaning, 10–250 in pigs 5 weeks post weaning and 50–250 in pigs 7 weeks post weaning (titer < 10 = negative). Five pigs had L. intracellularis specific antibodies with OD-values from 44% to 86% (OD-values < 7 = negative). Based on the investigations a diagnosis of non-specific colitis (NSC) was made.
The objective of the current report was to present a case of diarrhea in weaned pigs associated with non-specific colonic lesions of increased crypt depth and multifocal occurrence of subepithelial bacteria.
In Denmark, it is generally believed that proliferative enteropathy associated with L. intracellularis is the major cause of diarrhea in weaners and growers. However, other common enteric pathogens include E. coli, Brachyspira spp., and PCV2. Non-infectious causes of diarrhea include NSC (Thomson et al. Citation2007). NSC emerged in the 1980s, affecting growing pigs (12–40 kg bodyweight) (Thomson Citation2009). The condition is associated with diarrhea and reduced growth performance (Duncan and Lysons Citation1987), affecting 40–80% of a batch of pigs (Thomson et al. Citation2002). Unique pathological lesions have not been described, but mild to moderate colitis with mucosal hyperplasia, mononuclear cell infiltration and multifocal mucosal erosions have previously been reported (Thomson et al. Citation2002). Diagnosis of NSC relies on detection of pathological lesions consistent with NSC in the absence of pathogens like Salmonella spp., Yersinia spp., Brachyspira spp., L. intracellularis, or parasites (Thomson et al. Citation2007). However, NSC is considered a poor descriptive term (Thomson et al. Citation2002) and the condition and its diagnosis remain rather poorly defined.
Etiology and epidemiology of NSC is believed to be associated with feed composition, especially pelleted feed, wheat-based diets, and feed containing high levels of non-starch polysaccharides (Thomson et al. Citation2007). Recently, specific enzymes and application of barley instead of wheat have been observed to reduce the occurrence of NSC (Thomson Citation2009).
The laboratory examinations demonstrated that the common intestinal pathogens in Denmark were not involved or occurred in low prevalence. However, an infectious nature of the diarrhea could not be excluded. An extensive list of potential intestinal pathogens exists, but exhaustive laboratory examination including all potential intestinal pathogens is not economically possible in the field situation. Including histopathology in the diagnostic work up offered a non-specific method for detection of lesions compatible with different types of intestinal pathogens. In the current case, no lesions compatible with an infectious pathogen were demonstrated. However, absence of such lesions do not completely rule out an infectious cause of diarrhea. For instance, some pathogens are known (E. coli) or considered (L. intracellularis) (Guedes et al. Citation2010) to cause diarrhea without morphological intestinal changes. Other infectious pathogens may have similar abilities. The recurring nature of the diarrhea could be explained by virus-associated diarrhea, bacterial antibiotic resistance or caused by a too short antibiotic treatment. Furthermore, the identified feed-related problems may be considered to be a necessary but insufficient factor for triggering infectious diarrhea. However, the apparent restriction of the problem to diet number two and the recurring outbreaks of diarrhea support a feed-related cause. Diet number two contained a higher total level of protein and wheat. The diet also contained soybean protein, which has a lower digestibility than fishmeal. Total level and digestibility of protein has been reported to affect the intestinal microbiota (Heo Citation2010). Further, fermentation of undigested protein in colon results in production of toxic by-products (Heo Citation2010). This may provide an explanation for development of protein-associated diarrhea. The histopathological lesions of NSC with increased crypt depth and multifocal occurrence of different bacteria in lamina propria was apparently not associated to any intestinal infection. The subepithelial bacteria were considered to be of no significance by the investigating pathologist. The increased crypt depth may result from protein degradation in colon. Increased crypt depth has been considered to result from increased turnover rate of intestinal mucosa cells (Jin et al. Citation1994). It has been associated to diet rich in dietary fiber (Jin et al. Citation1994) and coarsely ground cereals (Brunsgaard Citation1998). The effect of fiber and starch is considered to be caused by short-chain fatty acids produced by carbohydrate fermentation (Sakata Citation1987). The current diets were not high fiber diets, but the feed particle size may explain part of the increased crypt depth. To the author's knowledge, association between non-infectious diarrhea, protein fermentation, and increased crypt depth in colon has not been investigated yet. Demonstration of increased crypt depth could potentially provide an additional tool for diagnosis of feed-related diarrhea. However, research is needed to investigate these associations and the occurrence of the demonstrated lesions in weaned pigs.
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