Which of the following malarial parasites has the longest incubation period ?

Options

A. P. vivax
B. P. ovale
C. P. malariae
D. P. falciparum

Answer

To determine which malarial parasite has the longest incubation period, we will analyze the incubation periods of each of the listed parasites one by one.

### Step-by-Step Solution:

1. **Understand the Incubation Period**:
- The incubation period is the time between the infection by a pathogen and the appearance of the first symptoms.

2. **List the Malarial Parasites**:
- The malarial parasites we need to consider are:
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae
- Plasmodium falciparum

3. **Identify the Incubation Periods**:
- **Plasmodium vivax**: The incubation period is approximately **12 to 17 days**.
- **Plasmodium ovale**: The incubation period is about **12 to 20 days**.
- **Plasmodium malariae**: The incubation period ranges from **13 to 28 days**, and it can extend up to **40 days** in some cases.
- **Plasmodium falciparum**: The incubation period is around **9 to 14 days**.

4. **Compare the Incubation Periods**:
- Now, we compare the ranges:
- Plasmodium vivax: 12-17 days
- Plasmodium ovale: 12-20 days
- Plasmodium malariae: 13-28 days (up to 40 days)
- Plasmodium falciparum: 9-14 days
- Among these, **Plasmodium malariae** has the longest incubation period.

5. **Conclusion**:
- Therefore, the malarial parasite with the longest incubation period is **Plasmodium malariae**.

### Final Answer:
**Plasmodium malariae** has the longest incubation period among the given malarial parasites.

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