A study on causes of cattle liver condemnation at an abattoir in Omdurman area, Khartoum State, Sudan.

BACKGROUND: Information obtained from abattoirs on the causes of liver condemnation is important in preventing the spread of diseases and for promoting food security. The current study reviews three years (2009 to 2011) postmortem inspection records of cattle slaughtered at an abattoir in Omdurman, Khartoum State, Sudan. The aim was to determine the prevalence of diseases and conditions that lead to liver condemnation. RESULTS: From a total of 234,175 cattle slaughtered, 8,910 (3.8%) livers were condemned due to several diseases/conditions mainly fasciolosis, cysticercosis, necrosis, abscess, calcification, hemorrhages, liver cirrhosis, hydatidosis, and other miscellaneous causes. Collectively, fasciolosis was the leading cause of liver condemnation and was responsible for 51.6 % of total liver condemnations followed by necrosis (18.6%), and cysticercosis (13.5%). CONCLUSIONS: Because of their zoonotic nature, the observed high frequency of some detected diseases/conditions is thought to pose a public health risk among consumers. This survey could be used as a regional baseline for future monitoring of control programmers against these liver diseases.

Partial hepatectomy for treatment of multiple liver abscess in a calf: a case report.

BACKGROUND: Umbilical vein bacterial infections may cause liver abscesses during bacterial ascent. A single liver abscess can be surgically treated by marsupialization, but a risk of recurrence or non-healing remains. Moreover, there is no effective treatment for multiple abscesses. CASE PRESENTATION: A 17-day-old Holstein female calf exhibited reduced general condition, swelling and drainage of the umbilicus, and pressure sores in the area of the carpus, resulting in reluctance to stand up. The umbilicus showed pain at palpation; deep abdominal palpation indicated a swollen umbilical vein coursing from the umbilicus toward the liver. Ultrasonography confirmed a swollen umbilical vein with pus accumulation and multiple abscesses in the liver. Contrast-enhanced computed tomography (CT) examination confirmed that the swollen umbilical vein with fluid continued to the liver, and multiple unenhanced lesions, most likely abscesses, were confirmed in the liver. Partial hepatectomy was performed to remove as many abscesses as possible. For the resection, a vessel sealing device (LigaSureTM) was used to excise a part of the left liver lobe. As we could not remove all the abscesses in the liver during the operation, cefazolin sodium (5 mg/kg) was administered for 14 days after surgery. Post-operatively, blood accumulation was observed in the abdominal cavity, but no signs of peritonitis were found. The calf returned to the farm on day 38 after surgery. Follow-up information was obtained after 1 year, and complications were not reported. CONCLUSIONS: To our knowledge, this is the first report of partial hepatectomy using a vessel sealing device for a calf with multiple liver abscesses. This case report suggests that the combination of partial hepatectomy and long-term administration of antibacterial drugs may restore the health of calves with multiple liver abscesses.

Leukotoxic activity of Fusobacterium necrophorum of cattle origin.

Fusobacterium necrophorum is a Gram negative, rod-shaped and aero tolerant anaerobe. In animals, it is an opportunistic pathogen frequently associated with necrotic infections, generally called necrobacillosis, such as calf diphtheria, foot rot and liver abscesses in cattle. Two subspecies exist: subsp. necrophorum and subsp. funduliforme. Among several virulence factors, leukotoxin (Lkt) is considered to be a major factor and a protective antigen. The objective of the study was to utilize BL3 cells and measure the release of lactic dehydrogenase to quantify Lkt activity of F. necrophorum. The assay was used to examine the effects of storage and handling conditions, growth media, polymyxin B addition on the cytotoxicity and evaluate Lkt activities of F. necrophorum strains isolated from bovine liver abscesses and foot rot. The Lkt activity peaked at 9 h of incubation. There was a significant decrease in the cytotoxicity measured in the samples after each freeze and thaw cycle. No difference was observed in the cytotoxicity for the samples handled aerobically versus anaerobically. Lkt activities of strains grown in anaerobic Brain-Heart Infusion broth were higher compared to Vegitone broth. A small reduction in the cytotoxicity activity was observed after the addition of polymyxin. The Lkt activity was consistently higher in strains of subsp. necrophorum than subsp. funduliforme of liver abscess origin. Among the strains isolated from cattle foot rot, Lkt activities of subsp. necrophorum strains appear to be much more variable. Use of BL3 cells in combination of lactic acid dehydrogenase assay appears to be a simple and valid assay to measure Lkt activity of F. necrophorum.

Alveolar echinococcosis in an Ontario dog resembling an hepatic abscess.

A boxer dog was evaluated because of lethargy, vomiting, and abdominal pain. Ultrasonography revealed multiple cystic structures in the abdomen. Exploratory laparotomy revealed 3 well-encapsulated hepatic masses and abdominal effusion with suppurative inflammation. Collectively, these findings suggested the hepatic masses were most likely abscesses. However, histologic examination of the hepatic masses revealed multi-cystic structures, consistent with alveolar echinococcosis. The diagnosis was confirmed by DNA sequencing. The dog was treated with daily albendazole, but within a few weeks exhibited adverse side effects. After 6 months, the dog's condition deteriorated, and it was euthanized.

Échinococcose alvéolaire ressemblant à un abcès hépatique chez un chien en Ontario. Un chien de race boxer fut évalué à cause de léthargie, vomissements, et douleur abdominale. Une échographie révéla de multiples structures kystiques dans l'abdomen. Une laparotomie exploratoire révéla trois masses hépatiques bien encapsulées et une effusion abdominale avec inflammation suppurative. Collectivement, ces données suggéraient que les masses hépatiques étaient fort probablement des abcès. Toutefois, l'examen histologique des masses hépatiques révéla des structures multi-kystiques, compatibles avec une échinococcose alvéolaire. Le diagnostic fut confirmé par séquençage d'ADN. Le chien fut traité avec de l'albendazole quotidiennement, mais en quelques semaines il montra des signes d'effets adverses. Après 6 mois la condition du chien se détériora et il fut euthanasié.(Traduit par Dr Serge Messier).

Multiple liver abscesses in a dog secondary to the liver fluke Metorchis conjunctus treated by percutaneous transhepatic drainage and alcoholization.

A 1-year-old German shepherd × husky cross dog was diagnosed with multiple liver abscesses and severe cholangitis secondary to the liver fluke Metorchis conjunctus. The dog was successfully treated with 2 percutaneous transhepatic drainage and alcoholization procedures, and a prolonged course of antibiotics and praziquantel.

Abcès hépatiques multiples chez un chien secondaire à une douve du foieMetorchis conjunctustraitée par drainage transhépatique percutané et alcoolisation. Un chien de race croisée Berger allemand et Husky âgé de 1 an a été diagnostiqué avec des abcès hépatiques multiples et une cholangite grave secondaire à la douve du foie Metorchis conjunctus. Le chien a été traité avec succès à l'aide de deux interventions de drainage transhépatique percutané et d'alcoolisation ainsi que d'un traitement prolongé aux antibiotiques et au praziquantel.(Traduit par Isabelle Vallières).

Hepatic abscesses in five outdoor-housed rhesus macaques (Macaca mulatta).

Hepatic abscesses are uncommon in non-human primates and usually occur as multifocal microabscesses originating from bacteremia. Necropsy, histopathology, and bacterial cultures were performed on five subadult to adult female rhesus macaques (Macaca mulatta) that died spontaneously. Necropsy findings included cavitating abscesses in the right central liver lobe of all five animals, with intralesional plant material in four animals. This is the first report of cavitating hepatic abscesses with intralesional plant material in non-human primates.

Development of an experimental model for liver abscess induction in Holstein steers using an acidotic diet challenge and bacterial inoculation.

Holstein steers (n = 40; initial BW = 84.9 ±â€…7.1 kg) were used to study the genesis of liver abscesses (LA) using an acidotic diet challenge with or without intraruminal bacterial inoculation. Steers were housed in individual pens inside a barn and randomly assigned to one of three treatments: (1) low-starch control diet comprised primarily of dry-rolled corn and wet corn gluten feed (CON); (2) high-starch acidotic diet with steam-flaked corn (AD); or (3) acidotic diet plus intraruminal inoculation with Fusobacterium necrophorum subsp. necrophorum (9.8 × 108 colony forming units [CFU]/mL), Trueperella pyogenes (3.91 × 109 CFU/mL), and Salmonella enterica serovar Lubbock (3.07 × 108 CFU/mL), previously isolated from LA (ADB). Steers in AD and ADB were fed the acidotic diet for 3 d followed by 2 d of the CON diet, and this cycle was repeated four times. On day 23, ADB steers were intraruminally inoculated with the bacteria. At necropsy, gross pathology of livers, lungs, rumens, and colons was noted. Continuous data were analyzed via mixed models as repeated measures over time with individual steer as the experimental unit. Mixed models were also used to determine the difference in prevalence of necropsy scores among treatments. Ruminal pH decreased in AD and ADB steers during each acidotic diet cycle (P ≤ 0.05). LA prevalence was 42.9% (6 of 14) in ADB vs. 0% in AD or CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD (P ≤ 0.04). Culture of LA determined that 100% of the abscesses contained F. necrophorum subsp. necrophorum, 0% contained T. pyogenes, 50% contained Salmonella, and 50% contained a combination of F. necrophorum subsp. necrophorum and Salmonella. The F. necrophorum subsp. necrophorum was clonally identical to the strain used for the bacterial inoculation based on phylogenetic analysis of the whole genome. This experimental model successfully induced rumenitis and LA in Holstein steers and confirms the central dogma of LA pathogenesis that acidosis and rumenitis lead to the entry of F. necrophorum into the liver to cause abscesses. Our findings suggest that an acidotic diet, in conjunction with intraruminal bacterial inoculation, is a viable model to induce LA. Further research is needed to determine the repeatability of this model, and a major application of the model will be in evaluations of novel interventions to prevent LA.

Liver abscesses (LA) in feedlots are costly to the beef industry. At harvest, LA cause an increase in liver condemnations, carcass trimming, and a decrease in quality grade. The objective of this research was to develop an experimental LA model in Holstein steers using an acidotic diet with and without intraruminal inoculation of bacteria involved in LA formation. These data suggest acidotic diet challenges in conjunction with bacterial inoculation were able to induce LA in Holstein steers. The acidotic diet alone caused reduced rumen content pH and caused rumen wall inflammation and damage, observed at harvest. Nonetheless, the addition of bacteria had a compounding effect on rumen damage. Both bacteria inoculated were isolated from 57% of LA suggesting they may work in synergy to form LA.

Evaluating the liver abscess microbiota of beef cattle during a reduction in tylosin supplementation shows differences according to abscess size and fraction.

Liver abscesses (LA) resulting from bacterial infection in cattle pose a significant global challenge to the beef and dairy industries. Economic losses from liver discounts at slaughter and reduced animal performance drive the need for effective mitigation strategies. Tylosin phosphate supplementation is widely used to reduce LA occurrence, but concerns over antimicrobial overuse emphasize the urgency to explore alternative approaches. Understanding the microbial ecology of LA is crucial to this, and we hypothesized that a reduced timeframe of tylosin delivery would alter LA microbiomes. We conducted 16S rRNA sequencing to assess severe liver abscess bacteriomes in beef cattle supplemented with in-feed tylosin. Our findings revealed that shortening tylosin supplementation did not notably alter microbial communities. Additionally, our findings highlighted the significance of sample processing methods, showing differing communities in bulk purulent material and the capsule-adhered material. Fusobacterium or Bacteroides ASVs dominated LA, alongside probable opportunistic gut pathogens and other microbes. Moreover, we suggest that liver abscess size correlates with microbial community composition. These insights contribute to our understanding of factors impacting liver abscess microbial ecology and will be valuable in identifying antibiotic alternatives. They underscore the importance of exploring varied approaches to address LA while reducing reliance on in-feed antibiotics.

Hepatic abscessation in dogs: A multicenter study of 56 cases (2010-2019).

OBJECTIVE: To investigate the clinical findings, treatment strategies, and outcomes in dogs with confirmed hepatic abscessation. DESIGN: Retrospective cohort study from 2010 to 2019. SETTING: Multicenter study. ANIMALS: Fifty-six client-owned dogs with hepatic abscessation confirmed by culture, cytology, or histopathology. MEASUREMENTS AND MAIN RESULTS: Dogs were presented for lethargy (39/56), hyporexia (31/56), and vomiting (26/56). Abnormal physical examination findings included increased temperature (41/56) and abdominal pain (22/54). CBCs revealed neutrophilia (31/49), toxic changes (25/49), anemia (28/49), and thrombocytopenia (23/49). Biochemical analyses revealed increased alkaline phosphatase (45/50), increased alanine aminotransferase (40/50), hypoalbuminemia (25/48), and hyperbilirubinemia (19/49). Hypoglycemia was found in 13 of 49 dogs. Hepatic abscesses ranging from 0.5 to 15 cm in diameter were identified ultrasonographically in 37 of 48 dogs; 19 of 37 had solitary abscesses, and 18 of 37 had multifocal abscessation. Escherichia coli was the most commonly cultured organism, isolated in 18 of 42 cases. Histopathology revealed underlying hepatic neoplasia in 10 of 47 dogs. Surgical management was performed in 41 of 49 dogs, and 35 of 41 survived to discharge. Medical management was performed in 8 of 49 dogs, and 5 of 8 survived to discharge. With univariate analysis, hypoglycemia and multifocal abscessation were associated with decreased odds of survival (odds ratio [OR]: 0.2, 95% confidence interval [CI]: 0.03-0.9, P = 0.04; OR: 0.07, 95% CI: 0.01-0.6, P = 0.02, respectively). With multivariate analysis, only multifocal abscessation was associated with decreased odds of survival (OR: 0.09, 95% CI: 0.01-0.87, P = 0.04). CONCLUSIONS: Hepatic abscessation, although rare, should remain a differential diagnosis for dogs presenting with nonspecific clinical signs and increase liver enzyme activities, especially with concurrent increased temperature and neutrophilia. Rate of survival to discharge for dogs in this study was consistent with previously reported survival rates, with 40 of 56 (71%) of the total population surviving to discharge. No variables assessed were able to predict survival to discharge; however, hypoglycemia and multifocal abscessation should be assessed in larger populations to determine prognostic significance.

Short communication: evaluation of an endotoxin challenge and intraruminal bacterial inoculation model to induce liver abscesses in Holstein steers.

Holstein steers (n = 40; initial body weight [BW] = 96.0 ± 10.5 kg) were individually housed in a climate-controlled barn to evaluate potential models for the genesis of liver abscesses (LA). In this 2 × 2 factorial, steers were balanced by BW and randomly assigned to one of two treatments: 1) intravenous saline injection followed by intraruminal bacterial inoculation with Fusobacterium necrophorum subsp. necrophorum (1 × 109 colony forming unit [CFU]/mL) and Salmonella enterica serovar Lubbock (1 × 106 CFU/mL; CON; n = 20 steers); or 2) intravenous injection with 0.25 µg/kg BW of lipopolysaccharide (LPS; Escherichia coli O111:B4) followed by intraruminal bacterial inoculation of F. necrophorum subsp. necrophorum (1 × 109 CFU/mL) and S. enterica serovar Lubbock (1 × 106 CFU/mL; LBI; n = 20 steers) and 1 of 2 harvest dates (3 or 10 d post LPS infusion). Body weights were recorded on days -4, -1, 3, and 10, and blood was collected for hematology on days -4, 3, and 10, relative to LPS infusion on day 0. Intraruminal bacterial inoculation occurred on day 1. Steers from each treatment group were harvested at two different time points on day 3 or 10 to perform gross pathological examination of the lung, rumen, liver, LA (if present), and colon. Feed disappearance was less for LBI than CON (P < 0.01); however, BW did not differ (P = 0.33) between treatments. Neither treatment nor time differed for hematology (P ≥ 0.13), and no gross pathological differences were noted in the lung, liver, LA, or colon (P ≥ 0.25). A treatment × harvest date interaction was noted for ruminal pathology in which LBI had an increased percentage of abnormal rumen scores on day 3 (P < 0.01). These results suggest that an LPS challenge in combination with intraruminal bacterial inoculation of pathogens commonly isolated from LA was not sufficient to induce LA in steers within 3 or 10 d (P = 0.95) when compared to CON. Further evaluation is needed to produce a viable model to investigate the genesis and prevention of LA in cattle.

Liver abscesses in feedlot cattle can cause a decrease in feed intake, average daily gain, feed efficiency, and hot carcass weight. At harvest, liver abscesses result in liver condemnations, carcass trimming, and a potential decrease in quality grade, with an estimated economic cost to packers of $41.6 million annually. Our objective was to evaluate an intravenous endotoxin challenge followed by intraruminal inoculation of bacteria commonly isolated from liver abscesses over a 10-d period as a potential model to understand the genesis and etiology of liver abscesses in cattle and evaluate possible preventative interventions. Results suggest that an endotoxin challenge in combination with intraruminal bacterial inoculation is not a viable model to induce liver abscesses in steers, and bacterial inoculation alone was insufficient to induce liver abscesses. The length of time necessary to induce liver abscesses is also unknown. Based on our results, more research is needed to develop a noninvasive model to induce liver abscesses in cattle.

Effect of increasing corn silage inclusion in finishing diets cattle with or without tylosin on performance and liver abscesses.

A pooled analysis was performed to evaluate whether corn silage fed at 15% or 45% of diet DM impacted liver abscesses prevalence at slaughter in five previous experiments. Cattle fed 15% corn silage had 7.8% abscessed livers compared to 4.1% for cattle fed 45% corn silage when all diets contained tylosin. While improved due to increased corn silage inclusion, the objective of the current finishing study was to determine the impact of silage inclusion in finishing diets with and without tylosin on performance and incidence of abscessed livers in beef cattle. A total of 640 (BW = 334 ± 25 kg) steers were used in a generalized randomized block design with a 2 × 2 factorial treatment design. Treatments included two concentrations of corn silage (15% and 45% of diet DM), with or without tylosin for liver abscesses. This study used 32 pens of cattle with 20 steers per pen and 8 pens per treatment. There was a tendency for an interaction for feed efficiency (G:F; P = 0.10) where cattle fed 15% corn silage had a 2% increase in G:F when tylosin was added to the diet, but no improvements in G:F were observed when tylosin was added to diets containing 45% silage. There was an interaction between silage and tylosin inclusion for abscessed livers (P = 0.05). Cattle fed 15% corn silage without tylosin had the greatest incidence of abscessed livers (34.5%) compared to other treatments (P = 0.05), and the incidence of abscessed livers was decreased to 19% if tylosin was fed with 15% corn silage. Feeding 45% silage was effective at lowering the incidence of abscessed livers (P = 0.05) which was 12.4%, regardless of whether tylosin was fed. Feeding corn silage at 45% of diet DM (77.5% concentrate) was as effective as feeding tylosin to cattle on a 92.5% concentrate diet. Feeding corn silage at greater inclusions decreased daily gain (P ≤ 0.01) but increased final body weight when fed to an equal fatness (cattle fed 45% CS were fed 28 d longer). Feeding corn silage at 45% was more economical compared to feeding 15% corn silage, especially as corn prices increase, provided shrink is well managed. Feeding elevated concentrations of corn silage may be an economically viable method to reduce incidence of liver abscesses without antibiotic use for smaller operations that can manage more corn silage in finishing diets.

Antibiotics are a very effective method to control liver abscesses for finishing cattle, which are thought to be due to high starch concentration and acidosis. Dietary roughage (forage) is used to control acidosis. As grain prices increase, feeding greater amounts of corn silage may be advantageous and silage can be an economical forage compared to other traditional forages like alfalfa. This study evaluated the impact of corn silage inclusion on performance and abscessed livers with and without the addition of antibiotics. As expected, feeding more corn silage decreased both gain and feed efficiency but also increased profitability. Feeding tylosin with a traditional inclusion of silage (15%) decreased abscessed livers from 34.5% to 19%. However, if cattle are fed more silage (45%) the incidence of abscessed livers was 12.4%, regardless of feeding tylosin or not.

Metabolome of purulent materials of liver abscesses from crossbred cattle and Holstein steers fed finishing diets with or without in-feed tylosin.

Liver abscesses in feedlot cattle are a polymicrobial infection with Fusobacterium necrophorum and Trueperella pyogenes as the primary and secondary etiologic agents, respectively. Cattle with liver abscesses do not exhibit clinical signs and the abscesses are detected only at slaughter. The objective was to conduct metabolomics analysis of purulent materials of liver abscesses to identify biochemicals. Liver abscesses from crossbred cattle (n = 24) and Holstein steers (n = 24), each fed high-grain finishing diet with tylosin (n = 12) or no tylosin (n = 12), were included in the study. Abscess purulent materials were analyzed by ultrahigh-performance liquid chromatography-tandem mass spectroscopy. A total of 759 biochemicals were identified and were broadly categorized into carbohydrates, energy metabolism pathways intermediates, peptides, amino acids and their metabolites, lipids and their metabolites, nucleotides, vitamins and cofactors, xenobiotics, and partially characterized molecules. The top 50 biochemicals identified included amino acids, lipids, nucleotides, xenobiotics, peptides, and carbohydrates and their metabolites. Among the 15 amino acid metabolites in the top 50 biochemicals, four were tryptophan metabolites, indoleacrylate, indolepropionate, tryptamine, and anthranilate. The 3-phenylpropionate, a product of phenylalanine metabolism, was the predominant metabolite in purulent materials. Between the four treatment groups, a two-way ANOVA analysis identified biochemicals that exhibited significant main effects for cattle type and in-feed tylosin use and their interactions. A total of 59 and 85 biochemicals were different (P < 0.05) between the cattle type (crossbred vs. Holstein steers) and in-feed tylosin use (tylosin vs. no tylosin), respectively. Succinate, an intermediate of lactate fermentation by some bacterial species, was one of the top 30 biochemicals that differentiated the four treatment groups. A number of lysophospholipids, indicative of bacterial and host cell membrane lyses, were identified in the purulent materials. In conclusion, to our knowledge this is the first report on the metabolome of liver abscess purulent materials and several biochemicals identified were related to metabolic activities of the bacterial community, particularly F. necrophorum and T. pyogenes. Biochemicals unique to liver abscesses that appear in the blood may serve as biomarkers and be of diagnostic value to detect liver abscesses of cattle before slaughter.

Liver abscesses in feedlot cattle, a consequence of feeding a diet of high-grain and low-roughage, are a mixed bacterial infection with Fusobacterium necrophorum, a ruminal bacterium as the primary causative agent. Cattle with liver abscesses do not exhibit clinical signs and the abscesses are detected only at slaughter. The study analyzed purulent materials of liver abscesses of feedlot cattle collected at slaughter for biochemical molecules. A total of 759 biochemicals were identified and a majority belonged to biochemical classes of lipids and amino acids and their metabolites. Biochemicals unique to liver abscesses that enter blood circulation may have the potential to be used as biomarkers in cattle with liver abscess before slaughter.

Unexpected finding of Fusobacterium varium as the dominant Fusobacterium species in cattle rumen: potential implications for liver abscess etiology and interventions.

Fusobacterium varium has been generally overlooked in cattle rumen microbiome studies relative to the presumably more abundant liver abscess-causing Fusobacterium necrophorum. However, F. varium was found to be more abundant in the rumen fluid of cattle and under culture conditions tailored to enrich F. necrophorum. Using near-full length 16S ribosomal ribonucleic acid sequencing, we demonstrate that F. varium grows under restrictive conditions commonly used to enumerate F. necrophorum, suggesting that previous F. necrophorum abundance assessment may have been inaccurate and that F. varium may be an underestimated member of the ruminal bacterial community. Fusobacterium varium were not as susceptible as F. necrophorum to in-feed antibiotics conventionally used in feedlots. Exposure to tylosin, the current gold standard for liver abscess reduction strategies in cattle, consistently hindered growth of the F. necrophorum strains tested by over 67% (P < 0.05) relative to the unexposed control. In contrast, F. varium strains were totally or highly resistant (0%-13% reduction in maximum yield, P < 0.05). Monensin, an ionophore antibiotic, had greater inhibitory activity against F. necrophorum than F. varium. Finally, preliminary genomic analysis of two F. varium isolates from the rumen revealed the presence of virulence genes related to those of pathogenic human F. varium isolates associated with active invasion of mammalian cells. The data presented here encourage further investigation into the ecological role of F. varium within the bovine rumen and potential role in liver abscess development, and proactive interventions.

The conventional method of liver abscess prevention in feedlot cattle is in-feed use of tylosin to target Fusobacterium necrophorum, which has been presumed to be the most common Fusobacterium species within the ruminal compartment. Our investigation into ruminal Fusobacterium, however, revealed a different species, Fusobacterium varium, to be abundant and ubiquitous in ruminal content samples. Furthermore, growth conditions tailored to enrich F. necrophorum consistently promoted growth of F. varium, and the bovine isolates tested had much lower susceptibilities to the commonly fed antibiotics tylosin and monensin compared to F. necrophorum. Fusobacterium varium is an emerging pathogen in humans and preliminary genome sequencing of two ruminal F. varium isolates revealed genes linked to pathogenicity. While the ecological role of F. varium in the rumen is still not fully understood, our findings draw attention to this pathogen and its potential implication in liver abscesses.

Effect of continuous in-feed administration of tylosin to feedlot cattle on macrolide and tetracycline resistant enterococci in a randomized field trial.

Liver abscess causes substantial economic loss to the beef cattle industry through liver condemnation, reduced animal performance, and carcass yield. Continuous in-feed use of tylosin is the most effective and a commonly used practice in beef cattle production to prevent liver abscess. However, such mass medication can increase the level of antimicrobial resistant bacteria. We investigated the effect of continuous in-feed use of tylosin in feedlot cattle on (i) concentrations and prevalence of erythromycin-resistant (ERYr) and tetracycline-resistant (TETr) enterococci; (ii) associated antimicrobial resistance genes (ARGs) for resistance; (iii) species distribution; iv) macrolide and tetracycline resistance gene concentrations; and (v) tylosin concentration. A cohort of weaned calves were randomized to receive tylosin-medicated feed (Tylosin; n = 10) or nonmedicated feed (Control; n = 10) for a full feedlot cycle. Feces, feed and pen-surface samples were collected and processed by culture, droplet digital PCR, and liquid chromatography/mass spectroscopy for bacterial enumeration, detection and characterization, ARG quantification, and tylosin concentration, respectively. Data were analyzed by mixed effects linear- or binary-regression models depending on the outcomes. Tylosin administration significantly increased fecal concentration (P < 0.001) and prevalence (P = 0.021) of ERYr enterococci and erm(B) gene concentration (P < 0.001), compared to the control group. Interestingly, tylosin administration significantly reduced (P = 0.037) fecal TETr enterococci concentration compared to the control group, with no significant effect (P = 0.758) on fecal tet(M) concentration. In both treatment groups, enterococci concentrations increased over time, peaking on 174 days in feed before returning to the baseline. ERYr enterococci concentration was significantly (P = 0.012) higher in tylosin medicated feeds, with no significant effect (P = 0.321) on TETr enterococci concentration. Pen-surface concentration of ermB was significantly (P = 0.024) higher in the tylosin group, with no significant effect (P > 0.05) on bacterial concentrations. Increased diversity and a shift in the composition of enterococcal species and ARGs were observed over time, although tylosin use did not significantly affect (P > 0.05) their prevalence. Tylosin concentration was significantly higher in the feces of tylosin administered cattle (P < 0.001) and medicated feed (P = 0.027), with numerically higher pen-surface concentration (P = 0.065) in the tylosin group. In conclusion, continuous in-feed use of tylosin in feedlot cattle increases macrolide resistant enterococci and its fecal excretion, while decreasing tetracycline resistance. Two medically important species, E. faecium and E. faecalis, were predominant regardless of resistance status or sample source. Risk-based approaches including label changes to limit tylosin use such as withdrawal period, and development of effective manure treatments are potential areas of research to reduce environmental and public health impacts.

Corynebacterium pseudotuberculosis liver abscess in a mature alpaca (Lama pacos).

A mature female alpaca was evaluated for weight loss and a 10-day history of anorexia, diarrhea, abdominal distension, and ventral edema. Ultrasonography revealed a hepatic mass, culture of which identified Corynebacterium pseudotuberculosis. This is the first reported case of an internal caseous lymphadenitis lesion resulting in clinical disease in a camelid.

Effect of Liver Abscessation on Carcass Outcomes.

For more than 80 years, liver abscesses have been documented to reduce beef system value. These infections of liver tissue result in poorer growth performance as evidenced by diminished live and carcass weights, leaner and lesser muscled carcasses, and greater rates of trim. Those negative outcomes are compounded by reduced animal and carcass value. As technology advances, methods to reduce and prevent liver abscesses should be a goal of scientists and producers worldwide.

Porcine iucA+ but rmpA- Klebsiella pneumoniae strains proliferate in blood of young piglets but are killed by IgM and complement dependent opsonophagocytosis when these piglets get older.

Klebsiella (K.) pneumoniae causes different diseases in humans and animals including the life-threatening liver abscess syndrome and septicemia, respectively. However, host-pathogen interactions of K. pneumoniae in porcine blood have not been studied. We investigated the working hypothesis that only distinct K. pneumoniae strains have the capacity to survive in porcine blood and that this feature is associated with specific molecular markers such as sequence type, profile of siderophore genes and the regulator of the mucoid phenotype (rmp). Furthermore, we characterize the immune response in growing piglets leading to killing of an invasive K. pneumoniae strain. The veterinary isolates showed great diversity in sequence types and profile of siderophore genes. Porcine isolates were mainly positive for the aerobactin gene iucA but did not carry rmpA and this genotype was associated with proliferation in blood of 4-week-old piglets. Supernatants of an iucA+ but not an iucA- strain boosted growth in porcine serum. Between four and eight weeks of age, piglets showed a prominent increase of IgM binding to K. pneumoniae. Immunglobulin M and complement were crucial for killing of a serum-resistant iucA+ porcine K. pneumoniae strain at eight weeks of age. Flow cytometry analysis confirmed induction of phagocytosis and oxidative burst mediated by serum samples of 8-week-old piglets. Based on our in vitro findings we propose that many porcine iucA+ rmpA- K. pneumoniae strains have the ability to cause bacteremia in young piglets in association with aerobactin-mediated iron acquisition and that this phenotype is lost as specific IgM increases after weaning.

Roughage and Dietary Influence on Liver Abscesses.

Many researchers have evaluated different nonantibiotic, dietary interventions to reduce liver abscessation including degree of grain processing, roughage particle size, ionophore inclusion level, and supplemental prebiotics or probiotics; however, these alternatives have been inconsistent in outcomes and have not proven to be successful. New technologies and methodologies that allow for description and characterization of the microbiome within cattle, their environment, and liver abscesses themselves may help elucidate the etiology of liver abscess formation and allow for targeting interventions that will provide solutions to replace or reduce antimicrobial use that is currently used for the reduction of liver abscess prevalence.

Liver Abnormalities in Cattle: Effect of Liver Abscessation on Growth and Productivity of Cattle.

Liver abscess has been identified in multiple classes of cattle, but cattle consuming higher energy diets may have greater prevalence of abscessation. The presence and severity of liver abscess has been associated with reduced dry matter intake, daily gain, and gain efficiency of individually fed animals, and as the prevalence of abscesses within pens of animals increases, growth performance worsens. Because of the importance of the liver to metabolism, damage due to abscess could negatively affect energy utilization. A preliminary analysis indicates severe liver abscess incidence increases the requirement of metabolizable energy for maintenance.

Pathogenesis of Liver Abscesses in Cattle.

Liver abscesses are a bacterial infection, which occurs because of entry, via portal vein, of pyogenic bacteria into the hepatic parenchyma. Liver abscesses are a polymicrobial infection; however, Fusobacterium necrophorum, a ruminal bacterium, is the primary etiologic agent. Ruminal acidosis disrupts the protective barrier function of the ruminal epithelium and facilitates entry and colonization of F. necrophorum in the ruminal wall and subsequent entry into the portal circulation. Virulence factors of F. necrophorum contribute to the evasion of host defense mechanisms and cause tissue damage to set up an infection in the liver. The potential role of the hindgut in pathogenesis remains to be investigated.