Prevention
of Toxo-How?? Pregnant women should be advised to avoid contact with cat litter
if at all possible. If they must change the litter they should do so daily wear
gloves and wash their hands afterward. They should always wash their hands
after preparing meat for cooking and should never eat raw or rare meat. Meat
should be cooked thoroughly until the juices are clear. Fruits and vegetables
also should be washed carefully to remove possible contamination by oocysts.
What is Congenital toxoplasmosis?It is an infection of
newborns that results from the transplacental passage of parasites from an
infected mother to the fetus. These infants usually are asymptomatic at birth but
later manifest a wide range of signs and symptoms including chorioretinitis
strabismus epilepsy and psychomotor retardation.
Most
tachyzoites are eliminated by the host’s humoral and cell – mediated immune
responses but not all tachyzoites. Some do remain as cysts in various parts of
body... Tissue cysts
containing many bradyzoites develop 7-10 days after systemic tachyzoite
infection. These tissue cysts occur in various host organs but persist
principally within the central nervous system (CNS) and muscle. The development
of this chronic state completes the nonfeline
portion of the life cycle.
What is not known to us?? What is enter-epithelial cycle? This enteroepitheial cycle begins with the ingestion of the
bradyzoite tissue cysts and culminates in the production of gametes. Gamete
fusion produces a zygote which envelops itself in a rigid wall and id secreted
in the feces as an unsporulated occyst. After 2-3 days of exposure to air at
ambient temperature the noninfectious
oocyst sporulates to produce eight sporozoite progeny. The sporulated occyst can be ingested by an intermediate host such as a
person emptying a cat’s litter box or a pig rummaging in a barnyard. It is in
the intermediate host that T gondii completes its life cycle.
What
is the prevalence / EPIDEMIOLOGY
T gondii
infects a wide range of mammals and birds. Its seroprevalence depends on the
locale and the age of the population. Generally hot arid climatic conditions
are associated with a low prevalence of infection. In the United States and
most European countries the seroprevalence increases with age and exposure. For
example in the United States 5-30 % of individuals 10-19 years old and 10-67%
of those >50 years old have serologic evidence of exposure seroprevalence
increases by ~1 % per year. In Central America, France, Turkey and Brazil the
seroprevalence is higher. There may be as many as 2100 cases of toxoplasmic
encephalitis each year in the United States.
Last Query by an old man?? What % of women
transmIts parasites to foetus if
acute infection occurs:-About one- third of all women who acquire infection
with T. gondii during pregnancy transmit the parasite to the fetus; the
remainder gives birth to normal uninfected babies. Of the various factors that
influence fetal outcome gestational age at the time of infection is the most critical.
Few data support a role for recrudescent maternal infection as the source of
congenital disease. Thus women who are seropostive before pregnancy usually are
protected against acute infection and do not give birth to congenitally
infected neonates.
Do not
scratch your head!!! How best to evaluate congenital infection?? . The
following general guidelines can be used to evaluate congenital infection.
There is essentially no risk if the mother becomes infected>26 months before
conception. If infection is acquired <6 months before conception the
likelihood of transplacental infection increases as the interval between
infection and conception decreases. In pregnancy if the mother becomes infected
during the first trimester the incidence of transplacental infection is lowest
but the disease in the neonate is most severe. If maternal infection occurs
during the third trimester the incidence of transplacental infection is greater
but the infant is usually asymptomatic at birth. Infected infants who are
normal at birth may have a higher incidence of learning disabilities and
chronic neurologic sequelae than uninfected children. Only a small proportion
of women infected with T. gondii develop clinical signs of infection. Often the
diagnosis is first appreciated when routine post conception serologic tests
show evidence of specific antibody.
What about Toxoplasmosis
in Immunocompetent patients
The most
common manifestation of acute toxoplasmosis is cervical lymphadenopathy. The
nodes may be single or multiple are usually nontender are discrete and vary in
firmness. Lymphadenopathy also may be found in sub occipital supraclacicular
inguinal and mediastinal areas. Generalized lymphadenopathy occurs in 20-30 %
of symptomatic patients.
Between 20
and 40 % of patients with lymphadenopathy also have headache malaise fatigue
and fever. A smaller proportion of symptomatic individuals have Myalgia sore
throat abdominal pain maculopapular rash meningoencephalitis and confusion.
Rare complications associated with infection in the normal immune host include
pneumonia myocarditis encephalopathy pericarditis and polymyositis .Symptoms
associated with acute infection usually resolve within several weeks although
the lymphadenopathy may persist for some months. In ones epidemic toxoplasmosis
is considered in the differential diagnosis, routine laboratory and serologic
screening should precede node biopsy.
What is the prevalence of Congenital
Toxoplasmosis in
other countries, many of them was Gig was positive!!!
Between 400
and 4000 infants born each year in the United States are affected by congenital
toxoplasmosis. Infection of the placenta leads to hematogenous infection of the
fetus. As stated earlier the proportion of fetuses that becomes infected
increases but the clinical severity of the infection declines as gestation
proceeds. Persistence of T. gondii can ultimately result in reactivation and further
damage decades later. Factors associated with relatively severe disabilities
include delays in diagnosis and in initiation of therapy neonatal hypoxia and
hypoglycemia profound visual impairment uncorrected hydrocephalus and increased
intracranial pressure. If treated appropriately upwards of 70% of children have
normal developmental neurologic and ophthalmologic findings at follow up evaluations.
Treatment for 1 year with Pyrimethamine and a sulfonamide is tolerated with
minimal toxicity.
How
frequent is Ocular infection in children whose mothers ARE Ig G positive or not
evaluated in Pre preg period/ at booking visit??
Infection
with T gondii is estimated to cause 35% of all cases of chorioretinitis in the
United States and Europe. Most ocular involvement is believed to be due to
congenital infection with a very low incidence following acquired infection.
Ophthalmologic examination
