Babesia gibsoni infection among dogs in the southeastern United States

OBJECTIVE: To identify subclinical Babesia gibsoni infection in American Pit Bull Terriers from the southeastern United States and to determine the genetic sequence of parasite DNA isolated from these dogs. DESIGN: Case series. ANIMALS: 33 American Pit Bull Terriers and 87 dogs of various other breeds. PROCEDURE: Blood smears were examined for microscopic evidence of the parasite, and DNA was extracted from blood samples and used in a polymerase chain reaction (PCR) assay designed to amplify the small subunit ribosomal RNA gene sequence of B. gibsoni. Amplification products of the expected size were sequenced, and sequences were compared with published sequences for B. gibsoni isolates. Hematocrit, platelet count, mean platelet volume, WBC count, and eosinophil count were compared between dogs with positive PCR assay results and dogs with negative results. RESULTS: Results of the PCR assay were positive for 18 of the 33 (55%) American Pit Bull Terriers, including all 10 dogs with microscopic evidence of parasitemia. Only 1 of these dogs was clinically ill at the time blood samples were collected. Results of microscopic evaluation of blood smears and of the PCR assay were negative for the 87 other dogs. Hematocrit and platelet count were significantly lower in dogs with positive PCR assay results than in dogs with negative results. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that American Pit Bull Terriers in the southeastern United States may be subclinically infected with B. gibsoni. However, subclinical infection was not identified in dogs of other breeds from the same geographic area.     

Clindamycin in the treatment of Babesia gibsoni infections in dogs

This report examines the effectiveness of clindamycin for the treatment of babesiosis in dogs (n=10) experimentally infected with Babesia gibsoni (B. gibsoni). Clindamycin (25 mg/kg body weight, per os, q 12 hours for 14 days) gradually reduced parasitemia levels and induced morphological changes that indicated degeneration of parasites (e.g., segmentation; size reduction; localization in the cell limbic and/or torn state of the nucleus; and swelling, decrease, or disappearance of the cytoplasm) in the majority of dogs. Clindamycin treatment reduced the clinical symptoms characteristic of Babesia infection, including anemia, anorexia, and listlessness. Clindamycin might be useful as a medicine for treatment of B. gibsoni infection.     

A 38-kDa protein from Babesia gibsoni and its antibody response in an experimentally infected dog

A cDNA encoding the Babesia bovis 12D3 antigen homologue was obtained by immunoscreening the expression library prepared from Babesia gibsoni merozoite mRNA. The complete nucleotide sequence of the gene was 1406 bp. Computer analysis suggested that the sequence contains an open reading frame of 1052 bp encoding an expected protein with a molecular weight of 36kDa. Based on homology analysis, this putative protein was designated as the B. gibsoni 12D3 antigen (Bg12D3). The Bg12D3 gene was expressed in the Escherichia coli BL21 strain, and the chronically infected dog serum reacted with the recombinant protein. The antiserum against the recombinant Bg12D3 protein can recognize a 38-kDa native protein, which is consistent with its expected size. Moreover, the purified recombinant proteins were used as the antigen to detect the antibody response in an experimentally infected dog by the enzyme-linked immunosorbent assay (ELISA). Our results indicated that the Bg12D3 protein was recognized by the host immune system and that it induced an antibody response in chronic B. gibsoni infection. These results allowed us to identify a new member of the 12D3 antigens and its characteristic immune response in canine B. gibsoni infection.     

Incidence of canine Babesia gibsoni infection and subclinical infection among Tosa dogs in Aomori Prefecture, Japan

To identify the incidence of Babesia gibsoni (B. gibsoni) in Aomori Prefecture, northeastern Japan, dogs with acute B. gibsoni infection were investigated at the Animal Teaching Hospital, Kitasato University, between April 2002 and March 2003. Eighteen dogs with acute B. gibsoni infection were recognized; they were all male dogs of the fighting dog breed Tosa. Their platelet counts were below normal and their packed cell volumes (PCVs) were at various levels. We collected blood samples from 141 Tosa dogs from Aomori Prefecture and used polymerase chain reaction assay to investigate the incidence of subclinical B. gibsoni infection. We also looked into the serological abnormalities associated with thrombocytopenia or anemia in subclinical infection. Forty-one of 87 dogs (47.1%) with histories of dog fighting, and one dog of 54 without a history of dog fighting were positive for B. gibsoni; that is, 42 of 141 dogs (29.8%) showed a positive result. The mean platelet counts of dogs with subclinical infection were significantly lower and levels of anti-platelet IgG were significantly higher than levels for dogs without infection. Anti-erythrocyte membrane IgG levels were significantly higher in dogs with subclinical infections, although mean PCVs were not significantly different. Tosa dogs from Aomori Prefecture, Japan, were highly infected with B. gibsoni subclinically and this pathogen might be successfully transmitted during dog fighting. Dogs with subclinical infections were at risk of chronic thrombocytopenia, which may be due to autoimmune mechanisms.     

Possible Emergence of Drug-Resistant Variants of Babesia gibsoni in Clinical Cases Treated with Atovaquone and Azithromycin

Background: There is no well-established treatment strategy for Babesia gibsoni infection. A new therapeutic protocol using atovaquone (ATV) and azithromycin (AZM) has been proposed, but there is concern about the possible induction of relapse and the emergence of ATV-resistant variants after treatment.
Objective: To evaluate the clinical use of combination therapy with ATV and AZM as a first-line treatment of clinical B. gibsoni infection in dogs, and to investigate the emergence of ATV-resistant variants.
Animals: Eight B. gibsoni naturally infected dogs showing signs of acute onset of disease.
Methods: Retrospective case study. Eight clinical cases received combination therapy with ATV and AZM at Kagoshima University Veterinary Teaching Hospital during 2007–2008, and their clinical courses and clinicopathological parameters were evaluated. In addition, alterations in the cytochrome b ( CYTb ) gene of B. gibsoni were analyzed by polymerase chain reaction and DNA sequencing techniques.
Results: All of the dogs responded well to the treatment, with rapid improvement in their clinical condition and hematological parameters. However, 5 of the 8 dogs relapsed after treatment. Analysis of the CYTb gene strongly suggested the emergence of ATV-resistant variants after treatment.
Conclusions and Clinical Importance: The combination of ATV and AZM can be used as a first-line treatment for dogs with babesiosis, but relapses occur. Attention should be paid to the possible in vivo selection of drug-resistant variants.     

Humoral and cellular factors affecting the neutrophil response of the locally immunised mammary gland to staphylococcal infection

Locally immunising the non-lactating ovine mammary gland by infusing killed Staphylococcus aureus enhances neutrophil accumulation in mammary secretion during subsequent staphylococcal infection. Immunological factors influencing this increased neutrophil response were studied in the present experiments. Glands locally immunised with killed Brucella abortus supported a greater neutrophil response to staphylococcal infection than did glands immunised with killed S. aureus. An enhanced neutrophil response to staphylococcal infection was recorded in 3 of 7 ewes locally immunised with zymosan. Passive immunisation by intramammary infusion of secretions from immunised glands conferred an enhanced neutrophil response during staphylococcal infection. Absence of haemolytic complement in secretions of immunised glands suggested complement was not implicated in the response. Secretions of immunised glands contained elevated concentrations of mononuclear cells. When exudates rich in mononuclear cells were established by infusion of endotoxin into non-immunised glands there was no increase in the neutrophil response to subsequent staphylococcal infection. However, when the mononuclear cell concentration was elevated by intramammary infusion of staphylococcal antigens in systemically immunised ewes there was an increase in the neutrophil response to subsequent infection. Thus humoral and cellular characteristics of the locally immunised mammary gland influence the kinetics of the neutrophil influx during staphylococcal infection.     

Feline hypertension: clinical findings and response to antihypertensive treatment in 30 cases

Systolic hypertension was diagnosed in 30 cats. At diagnosis, 16 of those were found to be in chronic renal failure only, while five were azotaemic and either receiving treatment for hyperthyroidism (four cases) or were untreated hyperthyroid cases (one case). Two cases were untreated hyperthyroid cases with no evidence of azotaemia and the remaining seven cases had no definitive diagnosis of the underlying cause of their hypertension. The successful treatment used for the majority of cases was amlodipine, which lowered systolic blood pressure from 202.5+/-16.8 to 153.2+/-21.6 mmHg (mean+/-SD; n=29) within the first 50 days. Each case was followed for at least three months, or to the end of its natural life, and each cat was re-examined every six to eight weeks. Systolic blood pressure was kept below a target value of 165 mmHg in 58 per cent of cases treated for three months or longer. At the time of writing, 19 of the cases had died or been euthanased with a median treatment time of 203 days, one case was lost to follow-up and 10 cases were still alive, nine of which had been treated for six months or more. Amlodipine can be used for long-term control of feline systemic hypertension.     

Possible sex differences in the susceptibility of calves to rotavirus infection.

The agar gel precipitation test was used to detect rotavirus antibodies in the serum of 562 calves and bovine rotavirus antigen in the feces of 347 calves. Significantly more females had rotavirus antibodies in the serum (P less than 0.01) and rotavirus antigen in the feces (P less than 0.1) than did male calves. Female buffalo calves were also found to be more susceptible than male buffalo calves to rotavirus infection.     

A comparison of methods to estimate the prevalence of ovine Johne's infection from pooled faecal samples

OBJECTIVE: To compare estimates of ovine Johne's infection prevalence produced by several alternate methods based on pooled faecal culture (PFC) results with prevalence estimates based on individual faecal culture (IFC). PROCEDURE: Seven methods for estimating prevalence of infection based on PFC results were incorporated in a computer program, including methods for imperfect test sensitivity and specificity, for variable pool size and a Bayesian method that incorporates prior knowledge about test performance and prevalence. These methods were then used to analyse PFC data at one observation 30 months post-vaccination in a field trial of a killed vaccine for the control of OJD, undertaken on three farms in New South Wales. RESULTS: Prevalence estimates, for three methods that assume a perfect test, were close to the IFC estimate, whereas for three other methods that assume an imperfect test, the estimated prevalence was generally higher than the IFC estimate. In comparison, the Bayesian approach produced more variable estimates that were substantially higher than the IFC estimate when an inappropriately high prior estimate of prevalence was used. CONCLUSION: Despite the limitations of each method, two methods provided accurate and reasonable estimates of the prevalence assessed by IFC in all instances, and are appropriate for the analysis of data from this vaccine trial. One of these methods also has the advantage of allowing for variable pool size. However, further research is needed to develop a method that will simultaneously account for variation in pool size and in test sensitivity and specificity.     

Broiler response model to estimate the economic importance of dietary feed enzymes

The purposes of this research were: 1) a bio-assay to evaluate the effects of 2 feed enzymes (Hostazym X) and Avizyme 1505) on the performance of Cobb broilers; and 2) to calculate the economic value from the technical response data. A broiler response model that includes benefits from improved performance and incorporates the expected changes in output from Hostazym X and Avizyme 1505 is presented. Each of the 4 diets [1) Basal (corn, dried grains with solubles, and soybean meal based diet with 1,360 kcal/lb), 2) Basal+ Hostazym X, 3) Basal+ Avizyme 1505, 4) Basal+30 kcal/lb] was fed to 8 pens of 24 straight run Cobb chicks. Supplementing the basal diet with either enzyme showed significant effects on growth and feed efficiency. Quadratic equations were fitted through the response points for 49 d broilers: Body weights and feed intakes were: Basal, 6.085, 11.446; Basal+ Hostazym X, 6.231, 11.359; Basal+ Avizyme 1505, 6.165, 11.288; Basal+30 kcal, 6.455lb, 11.535 lb, respectively. Target live weights were compared at 4, 6 and 8 lb, chicken prices at $0.68 and $1.0/lb and feed costs at $200 and $400/ton. The value of feed savings by adding Hostazym X ranged from $6.92/ton for 4.0 lb broilers fed $200 feed, to $17.52/ton for 8.0 lb broilers fed $400 feed. The value of extra meat by adding Hostazym X ranged from $21.19/ton for 6.0 lb broilers selling for $0.68/lb, to $32.76/ton for 8.0 lb broilers selling for $1.0/lb. The value of feed savings by adding Avizyme 1505 ranged from $5.58/ton for 4.0 lb broilers fed $200 feed, to $12.09/ton for 8.0 lb broilers fed $400 feed. The value of extra meat from AZ1 ranged from $16.97/ton for 6.0 lb broilers selling for $0.68/lb, to $24.95/ton for 8.0 lb broilers selling for $1.0/lb. The value of the extra salable meat from feeding enzymes is 2 to 3 times greater than feed savings. Enzyme value is directly dependent on the costs of feed and meat value, and indirectly on reduced environmental costs for feed production and reduced unutilized nutrients (pollution) per lb of meat (not included in this analysis).     

A cross-sectional pilot study to estimate the prevalence of and risk factors for leptospirosis in South-Western Victorian dairy herds, 2017

Leptospirosis is a zoonosis, found worldwide, affecting many species of animals. We conducted a cross-sectional study to estimate the prevalence of Leptospira borgpetersenii sv Hardjo and Leptospira interrogans sv Pomona in cattle in dairy herds in South-Western Victoria, Australia. Fifty-three herds were enrolled in the study. Urine samples were collected from 15 late-lactation cows in each herd. A questionnaire was provided to herd managers at the time of each herd visit, asking them to describe the methods they used for controlling leptospirosis, including vaccination. Urine samples were pooled at the herd level and tested for leptospira spp. using real time PCR. Urine samples from individual cows within the positive pooled samples were then tested for Leptospira Hardjo and Leptospira Pomona using qPCR. Four of the 53 herds showed positive leptospirosis results giving an apparent prevalence of 8 (95% CI 2–18) leptospira-positive herds per 100 herds at risk. Based on the 53 completed questionnaires, leptospirosis vaccination programs were not compliant with label directions in 36 of the 52 vaccinated herds: 69 (95% CI 55–81) of 100 herd managers that routinely vaccinated for leptospirosis did not comply with label directions. One herd was completely unvaccinated. Based on our findings, we estimate that approximately 10% of dairy farms in South-Western Victoria are likely to be infected with leptospirosis. While most herds are vaccinating for leptospirosis, most are not doing so according to label directions. We conclude that herd managers need to be better educated regarding leptospirosis vaccination programs.     

Survey to estimate prevalence of Leptospira interrogans infection in mature cattle in the United States.

A total of 5,142 kidney tissue samples and 5,111 serum samples from mature cattle in 49 states and Puerto Rico were collected at slaughter. Age of cattle ranged from 1 to 16 years (mean, 6.6 years). Leptospires were isolated from 88 (1.7%) kidney tissues, and 2,493 (49%) sera contained antibodies against 1 or more of 12 Leptospira interrogans serovars. Leptospires were observed by immunofluorescence in 41 (0.8%) kidney tissues. Using agglutinin-absorption tests, 73 (83%) isolates were identified as serovar hardjo, 11 (12.5%) as serovar pomona, and 4 (4.5%) as serovar grippotyphosa. By use of restriction endonuclease analysis studies of chromosomal DNA, all isolates differed from reference serovars but were identical to strains previously isolated from cattle or swine in the United States. Of the serovar hardjo isolates, 85% were identical to restriction endonuclease analysis type (genotype) hardjo-bovis A and 11 (15%) were identical to genotype hardjo-bovis B. Serovar pomona isolates were identical to genotypes kennewicki A (64%) or kennewicki B (36%), and serovar grippotyphosa isolates were identical to the RM 52 strain. Isolation rates were significantly (P less than 0.001) higher for beef cattle than for dairy cattle and were higher (P less than 0.001) for bulls than for cows. Combined culture and immunofluorescence results indicated that 2% of mature cattle were renal carriers of leptospires.     

Atrial fibrillation in horses: factors associated with response to quinidine sulfate in 77 clinical cases

Seventy-seven horses with atrial fibrillation (AF) were treated orally with quinidine sulfate (QS) at the University of Pennsylvania, School of Veterinary Medicine, Thirty-seven horses (48%) had adverse reactions to QS, the most common of which were nasal mucosal edema, anorexia, colic, and diarrhea. The mean highest daily QS dose was slightly greater in horses showing toxicity (P less than 0.1) and their conversion rate was less (P less than 0.05). A schedule of gradually increasing QS dose was time consuming, costly and not associated with fewer adverse reactions. Horses were compared by their response to QS: conversion for at least 12 months (Group I; 25 horses); reversion with 12 months (Group II; 8); nonconversion (Group III; 14). All horses with congestive heart failure (CHF) failed to convert. The mean age (P less than 0.05), total QS dose and highest daily QS dose (P less than 0.05) were significantly greater in Group III horses. The mean duration of signs before treatment and occurrence of adverse reactions to QS were greater in horses in Group II and III than Group I. (P less than 0.05). All horses in Groups I and II returned to performance, and many (81%) were successful. Most Group III horses (13/14) are known to have died. It was concluded that most horses with AF uncomplicated by CHF have a good prognosis when treated early with QS. Delayed QS therapy may reduce chances for conversion of AF or increase the probability of reversion.     

The porcine acute phase protein response to acute clinical and subclinical experimental infection with Streptococcus suis

The pig acute phase protein (APP) response to experimental Streptococcus suis (S. suis) infection was mapped by the measurement of the positive APPs C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp) and major acute phase protein (pig-MAP) and the negative APPs albumin and apolipoprotein (Apo) A-I. The aim was to elucidate the differences in the acute phase behaviour of the individual APPs during a typical bacterial septicaemic infection. Pigs were inoculated subcutaneously with live S. suis serotype 2 and blood was sampled before and on various days post inoculation (p.i.), until the pigs were killed and autopsied on day 14 p.i. Clinical signs (fever and lameness) were observed in four of the five inoculated pigs from day 2 p.i., and these pigs also had arthritic lesions at autopsy. CRP and SAA showed fast increases in serum concentrations, CRP being elevated from days 1 to 12 p.i. and peaking at 10 times the day 0-levels on day 1 p.i. SAA rose quickly to peak levels of 30-40 times the day 0-level on days 1-2 and returned to pre-inoculation level on day 5 p.i. Hp and pig-MAP showed slightly slower responses, both peaking around 5 days p.i. Hp was increased throughout the experiment with maximum levels around 10 times the day 0-levels, and pig-MAP was elevated on days 1-12 p.i. with peak levels of around seven times the day 0-levels. Apo A-I was decreased from days 1 to 8 and showed minimum levels of about 40% of day 0-levels around 1-2 days p.i. No clear pattern of changes in albumin levels could be identified. One pig, showing clinical signs on day 2 only, also showed an APP response, although of a relatively short duration, whereas three pigs presenting clinical signs for several days had a more protracted acute phase response. Remarkably, the one pig showing no clinical signs and no arthritic lesions showed an APP response comparable to that of the other, clinically affected pigs. Thus, both acute clinical and subclinical S. suis infection could be revealed by the measurement of one or more of the APPs CRP, SAA, Hp, pig-MAP and Apo A-I. The combined measurement of two or three APPs, including proteins with slow and fast kinetics, should be used to achieve the highest sensitivity for the detection of ongoing S. suis infection during a prolonged time period. A diagnostic tool based on such APP-measurements could considerably improve strategic control procedures for this important infection.     

Local and systemic immune response in pigs during subclinical and clinical swine influenza infection

Local and systemic immune responses in pigs intranasally (IN) and intratracheally (IT) inoculated with swine influenza virus (SIV) were studied. No clinical signs were observed in IN-inoculated pigs, while IT-inoculated pigs developed typical signs of influenza. Significantly higher titres of specific antibodies and changes of haematological parameters were found only in IT-inoculated pigs. Because positive correlations between viral titre, local cytokine concentration, and lung pathology have been observed, we hypothesise that both viral load and the local secretion of cytokines play a role in the induction of lung lesions. It could be that a higher replication of SIV stimulates immune cells to secrete higher amounts of cytokines. The results of the present study indicate that pathogenesis of SIV is dependent on both, the damage caused to the lung parenchyma directly by virus, and the effects on the cells of the host's immune system.     

Hepatozoon canis infection in dogs: clinical and haematological findings; treatment

Hepatozoon canis gametocytes were identified in the circulating neutrophils of six dogs from different parts of southern Israel. Clinical signs included fever, anaemia, anorexia, weakness of the hind legs and numerous brown dog ticks (Rhipicephalus sanguineus) on the skin surface. Parasitaemia varied from 6 per cent to 43 per cent of the circulating neutrophils. Two of these six cases also showed Ehrlichia morulae in the cytoplasm of leucocytes. Drug therapy with tetracycline hydrochloride 22 mg/kg, three times daily, and imidocarb dipropionate, 6 mg/kg, by subcutaneous injection, repeated after 14 days, was accompanied by clinical improvement and the depression of gametocyte parasitaemia.