Cas cliniques courants dans ma pratique vétérinaire au Maroc.
Mon expérience clinique très particulière de la theilériose bovine au Maroc.
Page de Lucien Mahin (partie vétérinaire).
Common clinical cases in my daily practice in Morocco.
My special field experience dealing with bovine theileriosis in Morocco.
Back to home-page of Lucyin Mahin (veterinary activity).
Sacwantès maladeyes ki dj' rescontere cobén come årtisse e Marok.
Mi apriyesse a médyî li five ås crexhioules des grossès biesses å Marok.
Hay ervoye sol pådje moennrece da Lucyin Mahin.
Nitrate poisoning in Doukkala.
Nitrate poisoning is observed following heavy rainfalls, from mid-december to mid-january.
In these weather conditions, natural grasses and seeded cereals have an intense and sudden growth. Moreover, farmers use massive doses of nitrogen fertilizers.
In natural grazings, intense growth of plants like Urtica spp and Malva alcea occurred on places where manure was gathered before being spread.
Spots of high soil nitrogen contents (deposits of manure) causing intense growing of Malva alcea.
Cases also occurred on alexandrian clover, or berseem (Trifolium alexandrinum) invaded with ray-grass (locally known as medhun).
Affected animals were mainly adult Freisian cows or crossbreds in a good body condition. Animal in late pregnancy were especially exposed to illness. All sick animals had nothing to eat but the aboved mentionned grasses or green forage.
Symptoms began in the mid to late afternoon, after day-through ingestion of dangerous plants. Affected animals where panting and refused to walk further on, then lied and could no longer stand up. Death generally occured at that early stage.
Clinical examination (in animal surviving that peracute phase) showed cardiac and respiratory acceleration and hypothermia (37-38°C). Pathognomonic was the brownish-pale coloration of the vaginal mucosa.
A spectacular outbreak of the disease occurred in rainfall season 1996-1997, where up to 150 fatalities (on some 50.000 cattle in the area) where recorded. Veterinarians were dubious in front of the disease, and many of them suspected Clostridium spp infection or anthrax, because of sudden death.
We incriminated nitrate because of the typical color of the mucosae and epidemiological features. The hypothesis was also supported Dr. Zidouh, Tnin Gharbia, who insisted on the cloudy sky wich had prevaled during the period.
Subsequently, a scientific team gave also support to our point of view.
Some veterinarians were reluctant to change their minds because the treatment they implemented following each one's own diagnosis leaded to clinical recovery.
We used methylene blue intravenously and sorbitol per os with similar good results. Nevertheless, we calculated afterwards that the methylene blue doses we administrated were 50 times less than the recommended doses.
It was concluded that all animals who escaped a critical point of methaemoglobin formation (the toxic compound formed in blood by action of nitrates and nitrites on haemoglobin) recovered spontaneously by quick physiological detoxication of methaemoglobin.
This explained the apparent efficacy of a wide variety of different medications, from intraruminal injection of penicillin to Long Action oxytetracyclin, or "vaccine-therapy" with enterotoxemia vaccines.
In such conditions of occurrence, the prevention was based on avoiding ingestion of the incriminated grasses or green cereals during three weeks. Cattle were adviced to grass in poorer lands when available. Otherwise they should be fed straw and concentrates in the morning before grazing moderately on dangerous pastures.
After mid-january, the poisonous effect of the same plants desappears.
Nitrates and nitrites are intermediar metabolites of plant nitrogen metabolism leading ultimatly to vegetable protein synthesis.
The same weather conditions re-occurred in winter 2002-2003. Fatal cases numbered 50-100 for the whole region. But veterinarians and agricultural authorities were more aware about the etiology, and provided preventive management advices to the farmers in January 2003.
L. Mahin, 15-04-03.
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