I am sorry to hear that your Shih Tzu has been unwell for sometime.
Bartonellosis is caused by infection with Bartonella bacteria and can affect
dogs, cats and humans as well as several other species. There are many different
species of Bartonella that make treatment somewhat difficult. The bacteria can
infect red blood cells as well as the cells lining blood vessels and the heart.
By living inside these cells it tends to avoid attack by the dogs immune system
and antibiotics. The bacteria is also very good at genetically altering itself
which further protects it from destruction. Infection occurs mainly from fleas,
ticks and biting flies so it is very important to maintain flea and tick
prevention in your dog – even if infection is already suspected. Diagnosis is
possible but can be very difficult without a sample of an organ or tissue which
is actively infected. Blood tests may reveal infection also but not reliable.
Dogs infected with Bartonella show various symptoms, including weight loss,
anaemia, hepatitis, bleeding from the nose, infection of the inside of the eye
(uveitis) or retina, infection of the heart or heart muscle and infection of
the joints. Symptoms may be subtle or severe and unfortunately not restricted
to just being due to Bartonella. Treatment is difficult as the antibiotics need
to be able to cross into the infected cells where the bacteria is living.
Azithromycin, doxycycline and enrofloxacin are all commonly used to treat
Bartonella infection and may be required for several weeks to kill the
bacteria. Dogs that are infected with Bartonella are susceptible to secondary
infections due to suppression of their immune system. I would recommend that if
no improvement has been seen in 8 months, then a review of the initial
diagnosis should occur. Alternatively there may be permanent organ damage which
is now causing symptoms and needs to be dealt with separately. I wish your
little Shih Tzu the best of luck in overcoming this illness.