Differential Diagnosis
- Cyanide poisoning
- Urea poisoning
- Pesticides
- Toxic gases (e.g., carbon monoxide, hydrogen
sulfide)
- Infectious or noninfectious diseases (e.g., grain
overload, hypocalcemia, hypomagnesemia,
pulmonary adenomatosis, or emphysema)
- Sudden unexplained deaths
Etiology
- Ingestion of nitrate
- rumen flora and anaerobic environment convert
nitrate -> nitrite
- nitrite + hemoglobin -> methemoglobin ->clinical
signs
1. History taking
- Sources of nitrate : plants(e.g. sudan, sorghum),
fertilizer or other chemicals, water from ponds that
receive extensive feedlot or fertilizer runoff
- Cattle are affected most frequently
2. Clinical examination
- Rapid weak heart beat
- Subnormal body temperature
- Muscular tremor
- Weakness
- Ataxia
- Brown, cyanotic mucous membranes
- Rapid difficult breathing
- Anxiety
- Frequent urination
- Death in 6-24 hr
3. Blood examination
- Blood containing methemoglobin usually has a
chocolate-brown color
- Dark brown discoloration of blood in moribund or
recently dead animals is not pathognomonic;
however, other methemoglobin inducers must be
considered
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Table : Differential diagnosis from other poisonings
| Substance Blood color |
| Nitrate/nitrite Brown |
| Sodium chlorate Brown |
| Nitrous dioxide, nitric oxide Slight brown |
| Cyanide Cherry red |
| Carbondioxide Dark |
| Carbonmonoxide Bright red |
4. Blood analysis
Specimen : blood, serum or plasma
Method : Chromatography
- > 20 ppm of nitrate in blood/ocular fluid=toxicosis
nitrate = nitrate nitrogen x 4.43
nitrite= nitrate x 0.74
- Plasma is the preferred antemortem specimen
(some plasma-protein-bound nitrate is lost in the
clotted blood)
5. Feed analysis
Specimen : feed and water
Method : Chromatography
- Total plant content of 6000-10000 ppm of nitrate
is potentially toxic
- Toxic level of nitrate in water for ruminant is
1,500-3,000 mg/L
6. Necropsy
- Pinpoint or larger hemorrhages on serosal
surfaces
- Perirenal edema
- Mesenteric edema
- Ascites
- Hydrothorax
7. Histopathological observation
- Degenerative and coagulative necrosis of proximal
and distal tubules of kidney
- Mild glomerular epithelial injury
- Granular cast in tubules of kidney
Control and treatment
- Slow IV injection of 1% methylene blue in distilled
water or isotonic saline should be given at
4-22 mg/kg BW or more
- Eliminate sources of nitrate
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