Efrén Díaz-Aparicio

Protection against brucellosis in goats, five years after vaccination with reduced-dose Brucella melitensis Rev 1 vaccine.

The protection conferred by the reduced-dose Rev 1 Brucella melitensis vaccine in goats that had been immunized 5 years previously was evaluated. Sixteen goats vaccinated 5 years before with Rev 1 (1×105 cfu) and 5 non-vaccinated goats were challenged with B. melitensis 16M (4×105 cfu) using the conjunctival route. After giving birth or aborting, the goats were sacrificed and tissue samples were taken for bacteriological study. The challenge strain was recovered in 12% of the animals from the vaccinated group, and in 80% of the control group. It is concluded, therefore that the use of reduced-dose Rev 1 protects goats vaccinated in endemic areas for at least 5 years after immunization.

Epidemiological study of Brucellosis in cattle, immunized with Brucella abortus RB51 vaccine in endemic zones

In this study the behavior of the Brucella abortus RB51 vaccine was evaluated in bovine herds, with different prevalence of Brucellosis. A prospective longitudinal study was made, in two dairies, one of low prevalence (9%) with 538 cows, and the other of high prevalence (15%) with 612 cows. The cattle were vaccinated twice 90 days apart with RB51 at a dose of 1×10(9)cfu/ml. The monthly incidence was determined during 660 days of observation. In the low prevalence dairy, all positive animals were eliminated as soon as they were diagnosed as positive and in this herd the number of new cases decreased to less than 1% between days 120, and day 660. In the dairy with high prevalence, positive cows were not eliminate resulting in the herd increasing its incidence by the end of the first year. Once positive animals were eliminated the incidence diminishes by day 660 to less of 1%. The odds ratio (OR) in the group of cows with abortion history, in the low prevalence dairy, was of 4.5 (1.2; 16.6), in the dairy ranch with high prevalence it presented an OR of 3.6 (1.5; 8.5). The conclusion from this study was that in brucellosis endemic zones, vaccination with RB51 by itself is not enough to control disease. It is mandatory that the initial elimination of all positive cows at the time of vaccination, the continued elimination of all new positive animals be adhered to for long periods of time.

PATHOGENIC LEPTOSPIRA SEROVARS IN FREE-LIVING SEA LIONS IN THE GULF OF CALIFORNIA AND ALONG THE BAJA CALIFORNIA COAST OF MEXICO

Abstract The California sea lion (Zalophus californianus), a permanent inhabitant of the Gulf of California in Mexico, is susceptible to pathogenic Leptospira spp. infection, which can result in hepatic and renal damage and may lead to renal failure and death. During summer 2013, we used the microscopic agglutination test (MAT) to investigate the prevalence of anti-Leptospira antibodies in blood of clinically healthy sea lion pups from seven rookery islands on the Pacific Coast of Baja California (Pacific Ocean) and in the Gulf of California. We also used PCR to examine blood for Leptospira DNA. Isolation of Leptospira in liquid media was unsuccessful. We found higher antibody prevalence in sea lions from the rookery islands in the gulf than in those from the Pacific Coast. Antibodies against 11 serovars were identified in the Gulf of California population; the most frequent reactions were against serovars Bataviae (90%), Pyrogenes (86%), Wolffi (86%), Celledoni (71%), and Pomona (65%). In the Pacific Ocean population, MAT was positive against eight serovars, where Wolffi (88%), Pomona (75%), and Bataviae (70%) were the most frequent. Serum samples agglutinated with more than one Leptospira serovar. The maximum titer was 3,200. Each island had a different serology profile, and islands combined showed a distinct profile for each region. We detected pathogenic Leptospira DNA in 63% of blood samples, but we found no saprophytic Leptospira. Positive PCR results were obtained in blood samples with high and low MAT titers. Together, these two methods enhance the diagnosis and interpretation of sea lion leptospirosis. Our results may be related to human activities or the presence of other reservoirs with which sea lions interact, and they may also be related to sea lion stranding.

Isolation of a field strain of Brucella abortus from RB51-vaccinated- and brucellosis-seronegative bovine yearlings that calved normally

A study was carried out in Pichucalco, Chiapas (Mexico) to determine whether recently calved cows or those that aborted shed Brucella. Serological diagnosis of brucellosis was made in all animals (209). Six of the cows that calved normally and two that aborted underwent a bacteriological study of milk and vaginal exudate. Brucella abortus was isolated from vaginal exudate samples in two 3- to 4-year-old seronegative first-birth cows that had calved normally. This was confirmed through bacteriological identification and PCR as a field strain and smooth phenotypes. We conclude that seronegative cows vaccinated with RB51 which calved normally and shed B. abortus in the vaginal exudate after calving could be a serious problem because these cows are overlooked in routine diagnoses and are a source of Brucella infection.

Isolation of Histophilus somni from the nasal exudates of a clinically healthy adult goat

MethodsThe nasal exudate from 42 goats of the Mixteca Region in the state of Puebla, Mexico, was evaluated. A strain was isolated after 4 days of incubation. This strain was identified according to its phenotypic characteristics and by means of a species-specific polymerase chain reaction (PCR), as well as by sequencing of the amplified product.ResultsThe species-specific PCR amplified a 407-bp fragment of 16S RNAr subunit, and the product sequencing revealed 100% homology with Histophilus somni 129PT. The nucleotide sequence was deposited in the GenBank under accession number HM032735.ConclusionThis is the first worldwide isolation of H. somni from nasal exudates of a clinically healthy goat.

Characterization of Escherichia coli strains from red deer (Cervus elaphus) faeces in a Mexican protected natural area

Escherichia coli is a commensal bacterium from the human and animal intestinal microbiota; however, some strains may be pathogenic and can cause a wide range of intestinal and extraintestinal diseases. The presence of pathogenic strains in wild animals, such as deer, may constitute a risk for humans and other animals. Thus, the aim of this study was to determine the antimicrobial resistance (AMR), serotype, phylogenetic groups and virulence genes (VGs) of 22 E. coli isolates obtained from red deer faeces (Cervus elaphus). Results showed that most isolates (17/22) were susceptible to the antimicrobials assessed, whereas only five of them were resistant to some of the tested antimicrobials (mainly to β-lactamics, and to trimethoprim/sulphamethoxazole). Regarding the phylogenetic groups, 19 isolates belonged to the B1 group and three to the B2 group. The identified VGs corresponded to stx1 (17/22), stx2 (12/22), estA (12/22), bfpA (6/22), and eae (4/22). Interestingly, hybrid strains containing VGs that belonged to STEC and EPEC (stx1, stx2, bfpA (n = 2) and stx1, bfpA (n = 1)) and to STEC and ETEC (stx1, estA (n = 1), stx2, estA (n = 1), stx1, stx2, bfpA (n = 6) and eae, stx1, stx2, bfpA (n = 1)) pathotypes were found. The identified serotypes were O:H21, O70:NM, O91:NM, O5:NM, O:NM, O23:H16, O23:H25, O38:H25, O6:H34, O6:NT and O75:H9. This work represents the first insight of potentially pathogenic E. coli strains in red deer from Mexico, and it establishes the importance of deer strain characterization. Moreover, the high frequency (12/22) of hybrid strains found in this study, along with a presumably pathogenic potential profile, could represent an additional risk for humans and animals, therefore further investigations on this issue would be needed.

Infection of California sea lions (Zalophus californianus) with terrestrial Brucella spp.

Infections with Brucella ceti and pinnipedialis are prevalent in marine mammals worldwide. A total of 22 California sea lions (Zalophus californianus) were examined to determine their exposure to Brucella spp. at San Esteban Island in the Gulf of California, Mexico, in June and July 2011. Although samples of blood, vaginal mucus and milk cultured negative for these bacteria, the application of rose Bengal, agar gel immunodiffusion, PCR and modified fluorescence polarization assays found that five animals (22.7%) had evidence of exposure to Brucella strains. The data also suggested that in two of these five sea lions the strains involved were of terrestrial origin, a novel finding in marine mammals. Further work will be required to validate and determine the epidemiological significance of this finding.

Stability of Antigen and Agarose Used in a Double Immunodiffusion Serologic Test for Brucella Ovis

cooked fish meal. Further questioning, however, revealed that prior to 1995 the owner fed bullheads (Ictalurus spp.) from a local lake for 8 consecutive years. These fish were very likely the source of the infection. These female mink probably contracted the infection when yearlings and spent their second year asymptomatically. The mink then developed fatal pancreatitis and peritonitis the third year following infection. Given the feeding practices in modern mink production, D. renale should be in the differential diagnosis as one of the causes of sudden death in adult animals.

Mycobacterium avium subsp. paratuberculosis down-regulates mRNA expression of iron-induced macrophage Ferroportin 1

Distributed under Creative Commons CC-BY 4.0 Abstract Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne’s disease. The mechanisms by which MAP is able to adapt to the innate host response are still unclear. We examined Ferroportin 1 (FPN1) mRNA expression levels via real-time PCR of the mouse macrophage cell line J774 that was incubated in the presence of Mycobacterium avium subsp. paratuberculosis (MAP) or MAP crude protein extract. Infection with live MAP decreased FPN1 mRNA levels in a multiplicity of infection (MOI)-dependent fashion. Macrophages infected with MOIs of 20:1 and 15:1 did not show any change in FPN1 gene expression, whereas MOIs of 10:1 and 5:1 induced a decrease of 50 and 80%, respectively. Macrophages treated with 50, 100, 150 and 200 μg/mL of MAP crude extract (ATCC19698) decreased FPN1 mRNA expression by 25%. Additionally, up-regulation of FPN1 mRNA by an iron overload treatment of 400 μM of ferric nitrilotriacetate (FeNTA) was abrogated by live MAP (MOI 20:1) by approximately 70%. Our data revealed an inhibitory effect of MAP on FPN1 mRNA and suggested a bacterial mechanism that may play a role in host iron regulation.