Administração repetida de doses não tóxicas de monofluoroacetato de sódio não protege contra a intoxicação por este composto em ovinos

Com o objetivo de avaliar se repetidas doses não tóxicas de monofluoroacetato de sódio (MFA) induzem resistência à intoxicação por essa substância, 18 ovinos foram distribuídos aleatoriamente em dois grupos experimentais de nove animais cada. Os ovinos do Grupo 1 ingeriram doses crescentes não letais de MFA por seis períodos: 0,05mg/kg por 5 dias; 0,08mg/kg por 4 dias; 0,08mg/kg por 4 dias; 0,1mg/kg por 3 dias; 0,1mg/kg por 3 dias e 0,25mg/kg por 3 dias. Entre o primeiro e o segundo período de administração e entre o segundo e o terceiro período os animais não receberam o MFA por 10 dias consecutivos; entre o terceiro e o quarto período e dentre os demais períodos de administração, os ovinos permaneceram 15 dias sem ingerir o MFA. Quinze dias após o último período de administração os ovinos foram desafiados com a dose única de 1mg/kg de MFA. O Grupo 2 não foi adaptado a ingestão de MFA, estes ovinos receberam dose única de 1mg/kg de MFA no mesmo período em que o G1 foi desafiado. No desafio sete ovinos do Grupo 1 apresentaram sinais clínicos da intoxicação e um ovino se recuperou. No Grupo 2 todos os animais manifestaram quadro clínico da intoxicação por MFA, no entanto, dois ovinos se recuperaram. Os coeficientes de mortalidade foram de 66,6% para o Grupo 1 e de 77,7% para o Grupo 2. Os resultados deste trabalho sugerem que a administração repetida de doses não tóxicas de MFA não protege contra a intoxicação aguda por este composto, portanto, outras alternativas para a profilaxia da intoxicação por plantas que contêm MFA deverão ser pesquisadas, principalmente a utilização intraruminal de bactérias que hidrolisam MFA

Identification of lamb flocks susceptible and resistant against Brachiaria poisoning

Abstract: This study was designed to assess the influence of genetic resistance against brachiaria poisoning in sheep. Two groups of sheep, one identified as susceptible (formed by two ewes and one ram) and the other as resistant against brachiaria poisoning (formed by three ewes and one ram) were selected. Sheep considered susceptible were those that presented clinical signs of brachiaria poisoning at any time of their life; resistant sheep were those that even raised on Brachiaria spp. pastures, did not developed any sign of the poisoning during their life. The offspring of the two flocks (15 lambs from the sensitive flock and 9 lambs from the resistant flock) were placed into brachiaria pasture (initially Brachiaria decumbens and B. brizantha,and only B. decumbens after weaning) and followed up during two years (2013-2014). The determination of protodioscin levels in B. decumbens pasture was performed only in 2014 and revealed significant amounts of the toxic principle. Eleven lambs of the susceptible group were affected to some degree of brachiaria poisoning and six died; no lamb of the resistant group was affected. Clinical signs consisted of varying degrees of subcutaneous edema of the face and, erythema and loss of hair of the ears, crusts on the skin of ears, around the eyes and on planum nasale, scar deformation of the ears, and bilateral ocular discharge; affected lambs also sought for shadowy shelters and they were poor doers. Several sheep recovered from the condition and then relapsed. Necropsy findings in six lambs included pale mucous membranes, emaciation, dermatitis, scar deformation of the ears, large yellow livers with marked lobular pattern, and moderate infestation by Haemonchus contortus. Histologically the liver lesions were similar in all necropsied lambs but with varying degrees of severity; they were consistent with brachiaria poisoning and included architectural disruption of hepatocellular trabecula, clusters of foamy macrophages occasionally forming multinucleated giant cells, swollen and vacuolated hepatocytes, crystals or negative images of crystals in the biliary system, bilestasis, bile duct proliferation and lymphoplasmacytic infiltrate in portal triads. The skin lesions were those of photodermatitis and included epidermal necrosis, hyperkeratosis and dermal neutrophilic infiltrate. The results of this study allow to conclude that there is a genetic related resistance to brachiaria poisoning in sheep since the progeny of resistant sheep did not manifest the poisoning. The use of resistant flocks in brachiaria pastures is suggested as a valuable option for the prevention of brachiaria poisoning in sheep

Blackleg in cattle in the state Mato Grosso do Sul, Brazil: 59 cases

ABSTRACT: This study aimed to review cases of blackleg (Clostridium chauvoei infection) diagnosed in cattle from Midwestern Brazil from 1994 to 2014 considering epidemiological, clinical, necropsy and histopathological findings. Also the following laboratory tests were used for the diagnosis of some cases of blackleg: microbiological culture and identification of the agent, microbiological culture and identification of the agent by the polymerase chain reaction (PCR), and identification of the agent in formalin fixed paraffin embedded tissues (FFPE). Criteria for presumptive diagnosis of blackleg included necrohemorrhagic emphysematous myositis consisting of inflammatory infiltrate, coagulative necrosis of myofiber, interstitial edema, hemorrhage, and gas bubbles between myofibers. Fifty nine cases from 51 outbreaks of blackleg were found, which corresponded to 1.1% of 5,375 cattle deaths investigated. In five of those outbreaks, samples of affected muscles cultures for the identification of pathogenic clostridia were made. Another three samples of similar material were cultured for clostridia with subsequent identification of the isolate by PCR. Twelve samples of FFPE affected muscle fragments were submitted to PCR for identification of the etiological agent. Except for January, cases were observed in each month of the year, with higher numbers in July-October. Most affected cattle were in the age of 7-12 years, but calves younger than 6 month-old and older than 24 months were also observed. Vaccination histories were scarce. In 32 outbreaks some vaccination history was available, but only in two of those vaccination has been carried out properly. In 56 six cases the skeletal muscles were involved. Muscles of the hind limbs were the most affected. In ten cases muscles of the tongue, myocardium and diaphragm were also affected. In three of the cases the visceral form was observed. Deaths occurred after a clinical course of 6-24 hours, but in most cases cattle were found death. Sudden death was the outcome in visceral cases (cardiac) blackleg. Clostridium chauvoei was confirmed to be the cause by culturing in 5 cases, and by PCR and histopatology in 8 cases. Bacterial culture followed by PCR did not demonstrate C. chauvoei. Calculation of the economic impact indicates that blackleg is a frequent disease in the state of Mato Grosso do Sul (MS) that inflicts significant economic loss. The amount of these losses would be reduced through proper vaccination programs against the prevalent strains of C. chauvoei in the region