Concept:
Different diseases are transmitted by specific vectors.
Step 1:
Leishmaniasis is transmitted by:
\[
\text{Sand flies}
\]
Thus:
\[
A \rightarrow III
\]
Step 2:
Scrub typhus spreads through:
\[
\text{Red mites}
\]
Thus:
\[
B \rightarrow I
\]
Step 3:
Trench fever is spread by:
\[
\text{Body louse}
\]
\[
C \rightarrow IV
\]
Rickettsial pox spreads through:
\[
\text{Mouse mite}
\]
\[
D \rightarrow II
\]
Step 4:
\[
A-III,\quad B-I,\quad C-IV,\quad D-II
\]
\[
\boxed{\text{Correct Option = (1)}}
\]