Marie-Eve Fecteau

Paratuberculosis in cattle.

Paratuberculosis remains one of the most important diseases of cattle worldwide. In cattle, the disease is debilitating and is characterized by weight loss and chronic diarrhea in the later stages of infection. However, cattle in the subclinical stages of the disease often show decreased milk production and are at higher risk for development of other common production diseases. Infections with Mycobacterium avium ssp paratuberculosis are difficult to control because of long incubation periods, the absence of clinical signs until advanced stages of the disease, and the lack of completely reliable diagnostic methods in the preclinical stages of the disease.

Antimicrobial Activity of Gallium Nitrate against Mycobacterium avium subsp. paratuberculosis in Neonatal Calves

BACKGROUND Mycobacterium avium subsp. paratuberculosis (MAP), the agent of Johnes disease in cattle, is a facultative intracellular bacterium that is dependent on ferric iron for its survival and replication. Gallium (Ga), a trivalent semimetal that shares many similarities with ferric iron and functions as an iron mimic has been shown to have in vitro antimicrobial activity against several microorganisms, including MAP. OBJECTIVES (1) To investigate the antimicrobial activity of Ga in calves experimentally infected with MAP; and (2) to monitor for potential adverse effects of Ga on calf health. ANIMALS Twelve Holstein calves. METHODS Randomized blind controlled experiment. Beginning at 10 days of age (study day 1), the experimental calves (n = 6) were treated with 20 mg/kg gallium nitrate daily for 45 days. On study days 4 and 5, all calves were challenged with a PO dose of a live field strain MAP. Treated calves were monitored daily for adverse effects. Calves were euthanized on study day 100, and 29 tissue samples and 1 fecal sample were collected from each calf. Samples were cultured for MAP by MGIT liquid culture system, Herrolds Egg Yolk Medium culture, or both. RESULTS No adverse effects were observed in the treated calves. Treatment was associated with a significant reduction in MAP tissue burden when compared with control calves (P = .017). CONCLUSIONS AND CLINICAL RELEVANCE Chemoprophylactic treatment of calves with Ga before and during the period of high susceptibility decreased MAP tissue colonization in experimentally infected neonatal calves.

Dysbiosis of the Fecal Microbiota in Cattle Infected with Mycobacterium avium subsp. paratuberculosis.

Johnes disease (JD) is a chronic, intestinal infection of cattle, caused by Mycobacterium avium subsp. paratuberculosis (MAP). It results in granulomatous inflammation of the intestinal lining, leading to malabsorption, diarrhea, and weight loss. Crohn’s disease (CD), a chronic, inflammatory gastrointestinal disease of humans, has many clinical and pathologic similarities to JD. Dysbiosis of the enteric microbiota has been demonstrated in CD patients. It is speculated that this dysbiosis may contribute to the intestinal inflammation observed in those patients. The purpose of this study was to investigate the diversity patterns of fecal bacterial populations in cattle infected with MAP, compared to those of uninfected control cattle, using phylogenomic analysis. Fecal samples were selected to include samples from 20 MAP-positive cows; 25 MAP-negative herdmates; and 25 MAP-negative cows from a MAP-free herd. The genomic DNA was extracted; PCR amplified sequenced on a 454 Roche platform, and analyzed using QIIME. Approximately 199,077 reads were analyzed from 70 bacterial communities (average of 2,843 reads/sample). The composition of bacterial communities differed between the 3 treatment groups (P < 0.001; Permanova test). Taxonomic assignment of the operational taxonomic units (OTUs) identified 17 bacterial phyla across all samples. Bacteroidetes and Firmicutes constituted more than 95% of the bacterial population in the negative and exposed groups. In the positive group, lineages of Actinobacteria and Proteobacteria increased and those of Bacteroidetes and Firmicutes decreased (P < 0.001). Actinobacteria was highly abundant (30% of the total bacteria) in the positive group compared to exposed and negative groups (0.1–0.2%). Notably, the genus Arthrobacter was found to predominate Actinobacteria in the positive group. This study indicates that MAP-infected cattle have a different composition of their fecal microbiota than MAP-negative cattle.

Treatment and Chemoprophylaxis for Paratuberculosis

There is no definitive cure for Mycobacterium avium subsp. paratuberculosis (MAP) infections, but several therapeutic agents may be used to alleviate clinical signs of Johne’s disease (JD) in ruminants of significant value. Treatment has to be maintained for the life of the animal and treated animals usually continue to shed MAP. No drugs are approved for treatment of JD in the United States; any drug use is “extra-label.” Isoniazid, rifampin, and clofazimine are most commonly used for treatment. Monensin, may aid in the prevention of infection in calves and to lower MAP fecal shedding in infected adult cattle.

Evaluation of the in vitro activity of gallium nitrate against Mycobacterium avium subsp paratuberculosis.

OBJECTIVE To evaluate the in vitro susceptibility of various field isolates of Mycobacterium avium subsp paratuberculosis (MAP) to gallium nitrate. SAMPLE 10 isolates of MAP, including 4 isolated from cattle, 2 isolated from bison, 1 isolated from an alpaca, and 3 isolated from humans. PROCEDURES The in vitro susceptibility to gallium nitrate was tested by use of broth culture with detection of MAP growth by means of a nonradiometric automated detection method. For each MAP isolate, a series of 7 dilutions of gallium nitrate (concentrations ranging from 200 to 1,000 μM) were tested. Gallium nitrate was considered to have caused 90% and 99% inhibition of the MAP growth when the time to detection for culture of the MAP stock solution and a specific concentration of gallium nitrate was delayed and was similar to that obtained for culture of the MAP stock solution (without the addition of gallium nitrate) diluted 1:10 and 1:100, respectively. RESULTS Gallium nitrate inhibited MAP growth in all 10 isolates. The susceptibility to gallium nitrate was variable among isolates, and all isolates of MAP were inhibited in a dose-dependent manner. Overall, the concentration that resulted in 90% inhibition ranged from < 200 μM for the most susceptible isolates to 743 μM for the least susceptible isolates. CONCLUSIONS AND CLINICAL RELEVANCE Gallium nitrate had activity against all 10 isolates of MAP tested in vitro and could potentially be used as a prophylactic agent to aid in the control of MAP infections during the neonatal period.

Comparison of the antimicrobial activities of gallium nitrate and gallium maltolate against Mycobacterium avium subsp. paratuberculosis in vitro.

Johnes disease (JD) is an enteric infection of cattle and other ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This study compared the antimicrobial activities of gallium nitrate (GaN) and gallium maltolate (GaM) against two field MAP isolates by use of broth culture. The concentrations that resulted in 99% growth inhibition of isolates 1 and 2 were, respectively, 636 µM and 183 µM for GaN, and 251 µM and 142 µM for GaM. For both isolates, time to detection was significantly higher for GaM than GaN. These results suggest that GaM is more efficient than GaN in inhibiting MAP growth in vitro.

Gastrointestinal spindle cell tumor of the rumen with metastasis to the liver in a goat

Many neoplasms have been reported in goats; however, neoplasia of the rumen is rarely reported. A 9-y-old castrated male pygmy goat was presented with a history of respiratory stertor, fever, and anorexia. A respiratory diagnostic work-up including skull and thorax radiographs and endoscopy revealed minor enlargement of the arytenoids but no other abnormal findings. After a month of little improvement on symptomatic treatment and worsening general health, the goat was euthanized. On autopsy, the forestomachs, liver, spleen, diaphragm, and the ventral and lateral aspects of the cranial third of the walls of the peritoneal cavity were adhered to one another by fibrinous and fibrous adhesions. Numerous firm, white, up to 2 cm diameter nodules were found throughout the liver. A large sessile mass extended from the rumen wall into the lumen. The rumen mass was a gastrointestinal stromal tumor with metastasis to the liver.

Serum and tissue concentrations of gallium after oral administration of gallium nitrate and gallium maltolate to neonatal calves.

OBJECTIVE To determine serum and tissue concentrations of gallium (Ga) after oral administration of gallium nitrate (GaN) and gallium maltolate (GaM) to neonatal calves. ANIMALS 8 healthy neonatal calves. PROCEDURES Calves were assigned to 1 of 2 groups (4 calves/group). Gallium (50 mg/kg) was administered as GaN or GaM (equivalent to 13.15 mg of Ga/kg for GaN and 7.85 mg of Ga/kg for GaM) by oral gavage once daily for 5 days. Blood samples were collected 0, 0.25, 0.5, 1, 2, 4, 8, 12, and 24 hours after Ga administration on day 1; 4 and 24 hours after Ga administration on days 2, 3, and 4; and 4, 12, and 24 hours after Ga administration on day 5. On day 6, calves were euthanized and tissue samples were obtained. Serum and tissue Ga concentrations were measured by use of mass spectrometry. RESULTS Data were adjusted for total Ga dose, and comparisons were made between the 2 groups. Calves receiving GaM had a significantly higher dose-adjusted area under the curve and dose-adjusted maximum serum Ga concentration than did calves receiving GaN. Despite receiving less Ga per dose, calves receiving GaM had tissue Ga concentrations similar to those for calves receiving GaN. CONCLUSIONS AND CLINICAL RELEVANCE In this study, calves receiving GaM had significantly higher Ga absorption than did calves receiving GaN. These findings suggested that GaM might be useful as a prophylactic agent against Mycobacterium avium subsp paratuberculosis infection in neonatal calves.