Is it morally wrong to kill a mosquito?

Probably not. How many brain cells does an animal need before it should have rights?

It doesn’t matter how many cells an animal has. Killing an animal unnecessarily is always evil.
But, mosquitoes are germs, not animals. No one should fight for the rights of germs. Mosquitoes cause thousands of deaths in India, not only of humans, but also of other animals. It would be extremely offensive and foolish to talk about giving rights to them. In other words, mosquitoes are evil, so we can kill them when they pester us.
But, if you don’t want to kill them, there is nothing wrong with that. There are lots of ways to avoid them without killing them. There are nowadays even cream that can be applied on the skin. Mosquitoes can’t bear the smell of the cream and they will stay away. You can also use anti-mosquito spray in your room to keep them away.

Is a mosquito really a “germ”? If it is about to bite you or you need to protect a baby or small child, Yes. Self defense is allowable in all cases, you have a right to live as well. Many mosquitoes are harmless but we are not scientists with psychic powers and cat like reflexes. So if you feel scared for yourself or others, then I can’t object.
Yes, there are many deadly diseases that are spread from certain species of mosquitoes, so always err on the side of caution.
The easiest way to protect yourself is to use window screens and keep a fan aimed at yourself. They cannot navigate winds higher than 1mph.

Mosquitoes are parasites. Parasites need a host or hosts to live, and may even kill it’s own hosts. It is ok to kill a parasite. Don’t lose sleep over this one.

In my opinion… SPLAT!!! — never mind.

Just an FYI…mosquitos are not parasites

and certainly not germs for that matter

Well, of course it’s not morally wrong to kill a mosquito. We extinguish millions of lives whenever we take antibiotics or cure a yeast infection. There has to be a line somewhere. I’m not going to walk around with pneumonia any more than you would. I like to put insects (ticks, mosquitoes,flies etc.) in that same category.