Question

Oral $\text{LD}_{50}$ (mg/kg) of malathion in buffaloes is}

• A. 100
• B. 200
• C. 10
• D. 55

Hint:

Organophosphate toxicities vary widely, but for malathion in ruminants, remember $100\text{ mg/kg}$ as a key threshold value. It is easy to remember as a round, baseline century mark.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The median lethal dose ($\text{LD}_{50}$) is a standard statistical measure used in toxicology to express the acute toxicity of a chemical substance.
It represents the dose required to kill $50\%$ of a test population under defined experimental conditions, typically expressed in milligrams of toxicant per kilogram of body weight ($\text{mg/kg}$).
In veterinary toxicology, determining specific species-dependent $\text{LD}_{50}$ values for pesticides like organophosphates is essential, as livestock sensitivity varies significantly across species.

Step 2: Detailed Explanation:
Malathion is an organophosphate insecticide widely used in agriculture and public health programs.
In target pests, it is converted to malaoxon, a highly active acetylcholinesterase inhibitor.
In mammals, malathion is generally considered to have lower toxicity than other organophosphates (like parathion or monocrotophos) because mammalian liver carboxylesterases rapidly detoxify it.
However, ruminants, including buffaloes and cattle, remain susceptible to accidental poisoning from contaminated feed or pasture.
Toxicological studies in domestic water buffaloes (Bubalus bubalis) have established that the acute oral median lethal dose ($\text{LD}_{50}$) of malathion is approximately $100\text{ mg/kg}$ body weight.
At this dose, clinical signs of organophosphate toxicity appear quickly, including:
- Profuse salivation, lacrimation, urination, and defecation (SLUD signs).
- Severe miosis, bronchospasm, and dyspnea.
- Muscle fasciculations, tremors, weakness, and eventual respiratory failure.
The values $200\text{ mg/kg}$, $10\text{ mg/kg}$, and $55\text{ mg/kg}$ do not represent the established oral $\text{LD}_{50}$ for this species.

Step 3: Final Answer:
The acute oral $\text{LD}_{50}$ of malathion in buffaloes is $100\text{ mg/kg}$ body weight.
Therefore, the correct option is (A).