Unfortunately, there are many potential reasons why kittens might die at 3 weeks old. It's impossible to give a specific answer without more information. Here are some common possibilities:
Infections:
* Feline Panleukopenia (Distemper): A highly contagious viral disease that can cause vomiting, diarrhea, and death, especially in young kittens.
* Feline calicivirus: Another common viral infection that can cause respiratory problems, oral ulcers, and death in kittens.
* Feline Herpesvirus: A virus that can cause respiratory problems, conjunctivitis, and death in kittens.
* Bacterial infections: Kittens can be susceptible to various bacterial infections, including E. coli and Salmonella.
Other factors:
* Feline Immunodeficiency Virus (FIV) or Feline Leukemia Virus (FeLV): These viruses can weaken a kitten's immune system and make them more susceptible to other illnesses.
* Parasites: Internal parasites like roundworms and hookworms can weaken kittens and lead to death, especially if untreated.
* Nutritional deficiencies: Kittens need a special diet high in protein and calories, and inadequate nutrition can make them vulnerable.
* Congenital defects: Some kittens are born with serious health problems that can lead to death at a young age.
* Trauma: Accidents or injuries can be fatal for kittens, especially if they are young and vulnerable.
* Cold temperatures: Kittens are very sensitive to cold and can easily become hypothermic.
* Poor hygiene: Dirty living conditions or lack of proper sanitation can contribute to the spread of infections.
Recommendations:
It's essential to consult with a veterinarian to determine the cause of death for your kittens. They can perform a necropsy (animal autopsy) to help identify the underlying cause.
To prevent future kitten deaths, consider:
* Vaccinating your cats: Vaccination can help protect your cats from deadly diseases like Feline Panleukopenia.
* Deworming your cats: Regular deworming is essential to prevent parasite infections.
* Providing a clean and safe environment: Keep your kittens' environment clean and free from potential hazards.
* Ensuring proper nutrition: Feed your kittens a high-quality, kitten-specific diet.
* Monitoring their health: Observe your kittens closely for any signs of illness.
Remember, it's always best to seek professional veterinary care when your kittens are sick or dying. They can provide the best possible care and diagnosis.