Risk factors associated with the seroprevalence of leptospirosis among students at the veterinary school of Zaragoza University

The prevalence and risk factors associated with leptospirosis were studied in veterinary students in Zaragoza. Sera were collected at the beginning and end of the academic year 1994 to 1995 and were tested by ELISA against a pool of Leptospira interrogans serovars bratislava, canicola, grippotyphosa, hardjo, icterohaemorrhagiae and pomona antigens. At the beginning of the study the prevalence was 8.14 per cent and at the end it was 11.4 per cent. The incidence of the disease during the study was 0.0394. Risk factors associated with leptospirosis included: taking the course specialising in food inspection and technology, on-farm work, contact with pets in general, and particularly carnivores, and contact with animal traders. The symptoms associated with the disease were myalgia and fever, and the treatment of the symptoms provided some protection.     

The susceptibility of domestic cats (Felis catus) to experimental infection with Leishmania braziliensis

Over the last few years, several cases of feline leishmaniasis (FL) with cutaneous and visceral forms have been reported around the world. Nonetheless, the real susceptibility of cats to infection with Leishmania spp. and the outcome of leishmaniasis in these animals are poorly understood. Experimental studies on feline models will contribute to the knowledge of natural FL. Thus, in order to determine the susceptibility of domestic cats (Felis catus) to experimental infection with Leishmania braziliensis, 13 stray cats were infected with 10(7) promastigotes by the intradermal route in the ear and nose simultaneously and followed up for 72 weeks. Soon after infection, the earliest indication of a lesion was a papule on the ear at 2 weeks post-infection (w.p.i.). The emergence of satellite papules around the primary lesion was observed about 4 w.p.i. Two weeks later these papules coalesced and formed a huge and irregular nodule. Thereafter, there was lesion dissemination to the external and marginal surface of the ipsilateral ear, and later to the contralateral ear. At 10 w.p.i., some nodules became ulcerated. Nose lesions presented a similar evolution. At both sites, the largest lesion sizes occurred at 10 w.p.i. and started to decrease 15 days later. Ear and nose nodules healed at 32 and 40 w.p.i., respectively. Specific L. braziliensis IgG antibody titers (optical density> or = 0.01 as positive result) were detected as early as 2 w.p.i. (0.09 +/- 0.02) in only three animals (23%), and all cats had positive titers at 20 w.p.i. (0.34 +/- 0.06). Only three animals (38%) continued to show positive serology at 72 w.p.i. (0.08 +/- 0.02). Up to that time, none of the cats had lesion recurrence. In a feline model of cutaneous leishmaniasis, it seems that there is no correlation between active lesions and positive serology. The implications of these data are discussed.     

Immunopathology of <Emphasis Type="Italic">Dirofilaria immitis</Emphasis> Infection

Heartworm disease caused by Dirofilaria immitis affects canine and feline hosts, with infections occasionally being reported in humans. Studies have shown that both dirofilarial antigens and those derived from its bacterial endosymbiont Wolbachia, interact with the host organism during canine, feline and human infections and participate in the development of the pathology and in the regulation of the host’s immune response. Both innate and acquired immune responses are observed and the development of the acquired response may depend on the host and, or on its parasitological status. This review aims at illustrating current research on the role of both D. immitis and Wolbachia, in the immunology and immunopathology of dirofilariosis.     

Effects of exogenous amylase on the in vitro digestion kinetics of whole-crop maize silages made from flint or dent grain type at different phenological stages grown in tropical condition

The effect of exogenous amylase on the in vitro rumen digestion kinetics of whole-crop maize silage made from dent (RB9004) or flint grain type (RB9308) was evaluated at different phenological stages: soft dough (SOD), early dent (EAD), ½ milkline (½M) and ¾ milkline (¾M). Forage was harvested from 70 to 110 days after sowing. Two rumen-cannulated cows receiving or not exogenous amylase (0.7 g/kg dry matter—DM, provided to achieve 396 kilo Novo units of amylase activity/kg of TMR DM) were used as donor of ruminal fluid. The in vitro gas production kinetics was evaluated according to a dual-pool logistic model. The chemical composition and gas production kinetics were affected by the hybrid and phenological stages. The flint hybrid had lower range for chemical analysis among physiological stages. Harvesting at ½M and ¾M improved DM content, bromatological composition and silage quality parameters compared to dent or flint types. Amylase (i) increased methane (CH₄) production and in vitro dry matter digestibility (IVDMD) in ½M stage, (ii) improved digestion kinetics by reducing lag time and increasing total gas production and fermentation rates of non-fibrous carbohydrates (NFC) and fibrous carbohydrates (FC), and (iii) increased extent and fermentation rate of NFC and increased fermentation rate of FC fraction in whole-crop maize silages produced from dent or flint types in all phenological stages. Harvesting between ½M and ¾M is the best phenological stage to improve chemical composition and silage quality parameters. Exogenous amylase showed improvements on fibre digestion of silages at ½M and ¾M phenological stages in both grain types of corn.     

Breeding objectives of Brangus cattle in Brazil

Our goal was to define a breeding objective for Brangus beef cattle in Brazil. Bioeconomic models were produced and used to estimate economic values (EVs). The scenarios simulated were typical full-cycle beef production systems that are used in tropical and subtropical regions. The breeding objective contained pregnancy rate (PR), warm carcass weight (WCW), mature cow weight (MCW), number of nematode eggs per gram of faeces (EPG) and tick count (TICK). Two models were used in series to estimate the EV. A deterministic model was used to simulate effects of PR, WCW and MCW on profitability with a constant parasite load. Subsequently, stochastic models were used to estimate economic values for TICK and EPG as consequences of their environmental effects on weight gains, mortality and health costs. The EV of PR, WCW, MCW, EPG and TICK, was US$1.59, US$2.11, −US$0.24, −US$5.35 and −US$20.88, respectively. Results indicate positive emphasis should be placed on PR (12.49%) and WCW (65.07%) with negative emphasis on MCW (13.92%), EPG (2.77%) and TICK (5.75%). In comparison with the indexes usually used, these results suggest a reformulation in the selection indexes of the beef production system in tropical and subtropical regions in order to obtain greater profitability.     

Evaluation of antiviral activity of phenolic compounds and derivatives against rabies virus

Human rabies is a viral disease with a great impact on public health, mainly on account of its fatal course in the majority of cases. Despite the well-established prophylaxis by immunization, rabies is believed to be responsible for 40,000-70,000 human deaths per year, mostly in endemic areas. Palliative support and experimental protocols to avoid death have been employed with no expressive results, with the exception of a recent human case of recovery from rabies. No antiviral drugs are currently available to fight against this infection. In combination with the prophylaxis, an antiviral drug would be useful for human rabies treatment, providing enhanced protection against the encephalitis caused by the virus. Phenolic compounds are derived from the secondary plant metabolism, although they can also be obtained by synthetic processes. Many studies have shown a great range of pharmacological effects for these substances, including vasodilatation, antiallergenic, antiinflammatory and antiviral properties, among others. In this study, the potential in-vitro anti-rabies activity of 24 synthetic phenolic compounds was evaluated using McCoy cells and PV rabies strain. The cytotoxicity (CC50) was assayed by the MTT method and the antiviral activity (IC50) was estimated by the inhibition of viral cytopathic effects. Isoprinosine and ketamine were used as positive controls. The tested compounds showed selectivity indices (SI=CC50/IC50) ranging from 1.0 to 3.9. Six phenolic compounds failed to inhibit the cytopathic effect to any degree, and four showed SI > or = 3.0. According to these results, some probable structure-activity relationships are suggested. It was observed that the presence of free hydroxyl and ether groups influenced the anti-rabies activity. However, additional studies are required to establish these relationships.     

Is Wolbachia complicating the pathological effects of Dirofilaria immitis infections?

Human and animal parasitic filarial nematodes, which often are the cause of severe disease, harbor intracellular bacteria of the genus Wolbachia (Rickettsiaceae). It is thought that these bacteria play an important role in the pathogenesis and immune response to filarial infection. In order to determine the possible role of Wolbachia in heartworm disease, dogs naturally infected with Dirofilaria immitis were studied for specific antibody response to Wolbachia surface protein (WSP). Antibody subclasses were analyzed to determine immune response polarization. Dogs that died from heartworm disease were necropsied, and various organs were studied by immunohistochemistry to determine whether Wolbachia-derived molecules were present in tissue from infected dogs. Humoral response to the WSP was present in all infected dogs and appeared to be predominantly of the Th1-type. Several organs, including lung, liver, and kidney, contained positive-staining cells for WSP, confirming that the canine host does come into contact with Wolbachia-derived molecules.     

Bovine Oocyte Quality in Relation to Ultrastructural Characteristics of Zona Pellucida,Polyspermic Penetration and Developmental Competence

In the present study, the effect of bovine oocyte quality related to ultrastructural characteristics of zona pellucida (ZP), polyspermic penetration and embryo developmental competence was evaluated. Cumulus–oocyte complexes were punctioned from 453 ovaries, classified as 1, 2, 3 and 4 according to their morphological aspect, matured for 24 h and then divided into two groups. In group A, oocytes were fixed in 2.5% glutaraldehyde and 0.1 m sodium cacodylate and examined under a scanning electron microscope. Photomicrographs were taken and ZP’s pores were evaluated in squares of 6.4‐μm width. In group B, oocytes were fertilized in vitro. After 48 h, non‐cleaved oocytes were fixed for polyspermy evaluation. On days 7, 9 and 10, embryos were classified as developed (blastocysts and hatched blastocysts). Results showed that quality 1 oocytes revealed a ZP pore diameter of 0.50 ± 0.07 μm, which was smaller than the observed on oocytes of quality 2 (0.83 ± 0.10 μm), quality 3 (1.02 ± 0.22 μm) and quality 4 (1.38 ± 0.59 μm) (p ≤ 0.05). For In Vitro Fertilization (IVF), results showed that embryos originating from oocytes classed as 3 and 4 had lower cleavage rate (68.4% and 43.8%) than those belonging to class 1 and 2 (79.5% and 69.3%) (p ≤ 0.05). None oocyte classified as 3 and 4 developed to hatch blastocysts, while for oocytes belonging to quality 1 and 2, these values were, respectively, 15.2% and 12.5%. Concerning polyspermy, oocytes class 1 and 2 had lower polyspermic penetration than those belonging to class 3 and 4 (respectively 4.1%, 4.5%, 11.1% and 9.8%, for class 1, 2, 3 and 4). In conclusion, the present study demonstrated that oocytes with low qualities result in lower developmental competence and with high percentage of polyspermy after IVF, which can be the result of the ZP structure such as the number and the pore’s diameter.     

High mortality and lesions of the central nervous system in trypanosomosis by Trypanosoma vivax in Brazilian hair sheep

Here, we report an outbreak of Trypanosoma vivax-induced trypanosomosis in Brazilian hair sheep on a farm in Paraíba state, a non-endemic region in northeastern Brazilian. Of 306 total sheep, 240 showed clinical signs and 216 died. Clinical signs included anorexia, lethargy, anemia, rough hair coat, weight loss, submandibular edema, abortion, and in some cases, neurological signs such as head pressing, lateral recumbence, paddling movements and muscle tremors. T. vivax was identified by blood smear analysis and polymerase chain reaction (PCR). At necropsy, animals exhibited watery blood, pale tissue coloring, and the presence of liquid in the peritoneal cavity and pericardial sac. Histologically, nonsuppurative myocarditis and meningoencephalitis with areas of malacia were observed. After treatment, no parasites were detected by blood smear analysis or PCR. Cattle and buffalo that remained in the same pasture were also infected but presented with asymptomatic infections. Epidemiological data suggest that T. vivax was introduced to the farm and the susceptible flock by buffalos that were asymptomatic carriers of the infection; T. vivax was most likely transmitted by Tabanus spp. bites and also iatrogenically.