Ocular Toxoplasmosis · diagnosis of atypical ocular toxoplasmosis and revealed that real-time PCR...
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Transcript of Ocular Toxoplasmosis · diagnosis of atypical ocular toxoplasmosis and revealed that real-time PCR...
Ocular Toxoplasmosis
Dr. Bahman Rahimi Esboei
Toxoplasmosis
Toxoplasma gondii: an obligate intracellular protozoan parasite with global
distribution
Toxoplasmosis is a parasitic disease that results from infection with the
Toxoplasma gondii parasite
This parasite have 3 morphological forms that all forms can cause the
transmission and infection
Clinical manifestation:
These symptoms can last for a month or more and usually resolve on their own:
• Fever.
• Swollen lymph nodes, especially in the neck.
• Headache.
• Muscle aches and pains.
• Sore throat.
Weakened immune systems:
• Brain inflammation, causing headaches, seizures, confusion and coma.
• Lung infection, causing cough, fever, and shortness of breath.
• Eye infection, causing blurry vision and eye pain, loss vision.
Ocular Toxoplasmosis
The most common cause of eye inflammation in the world.
Congenital & Acquired
Immune responses of the host appear to induce conversion of the parasitic
forms, from tachyzoites to bradyzoites and their encystment
The prevalence of the OT is variable in different populations and is estimated
from 0.3 to 1 % in Europe and North America
A comparable study revealed that the risk of developing of this disease is 18
and 382 in 100,000 individuals in UK and West Africa, respectively
There is not a comprehensive study about the prevalence of OT in Iran
Epidemiology
Pathogenesis
The retinochoroiditic scar of toxoplasma may harbor the toxoplasma cyst, and the organism may stay viable in the tissue for many years.
Inflammation in in inner layers of the retina are commonly seen.
The lesion may remain active for several weeks, undergoes healing, and forms a pigmented scar in the retina.
Rupture of the cyst may lead to the release of toxoplasma organisms and recurrence of retinochoroiditis.
Reactivation of a congenital infection was traditionally thought to be the most common cause of ocular toxoplasmosis, but an acquired infection is now considered to be more common.
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Route of ParasiteHow reach to the eyes?
Bloodstream:
The most likely way of transmitting the parasite to the eye area is through the
blood vessels, which initially causes inflammation in the choroidal area and is
then transmitted to the retina.
Nerve fibers:
Because the Toxoplasma parasite has a particular interest in the central
nervous system, since the optic nerve is the most important and active nerve
fiber in the body, and because of its close proximity to the eye, it is another
transmitted option.
The prognosis for ocular toxoplasmosis is dependent on what part of the eye is affected.
Prognosis
Scar around the optic disk:vision loss may be severe.
Damage to the macula and optic nerve:Permanent Vision loss
Inflammation in macula or the optic nerve:Abnormal vision (blurriness, loss)
In individuals with a normally functioning immune system and mild symptoms that do not threaten the function of the eye, treatment may not be needed and symptoms may resolve within 4-8 weeks.
Treatment
Other medications that have been used in individuals with ocular toxoplasmosis include the antibiotics clindamycin, azithromycin, and trimethoprim-sulfamethoxazole and the steroid dexamethasone.
Typically, the anti-parasitic medication pyrimethamine is utilized in combination with the antibiotic sulfadiazine and corticosteroids.
For cases in which there is a potential for vision loss, treatment may involve the use of anti-parasitic medications, steroids, and antibiotics.
Serological Techniques:
• ELISA (IgG, IgM, IgA), IFA, IHA, DAT, IgG avidity, CLIA and Goldmann-Witmer
coefficient (GWC)
Culture:• In-vivo• In-vitro
Imaging:OCTB-Scan
Technique DNA Targets Sensitivity Specificity
Conventional
PCR
B1, RE, ITS1,
SAG1, SAG2,
BAG1, GRA1
10-100%
105- 109 Tachyzoites/ml
85-100%
Nested PCR B1, RE, 18s rRNA 5-200 fg genomic DNA
103-105 Tachyzoites/ml
95- 100%
Real Time
PCR
B1, RE, SAG1,
BAG1
1–50 fg of genomic
DNA/10–103
Tachyzoites/ml
98- 100%
LAMP B1 gene, SAG1,
SAG2, RE, GRA1
10 fg of genomic
DNA/1–10 tachyzoites/
ml
95- 100%
Ali Rostami, Advances in serological, imaging techniques and molecular diagnosis of Toxoplasma gondii infection. Infection, 2018
Molecular Techniques
Among various molecular technics, LAMP is a popular technique because of its
sensitivity, specificity and isothermal conditions, which dont need for
specialized equipment (Notomi. 2000)
Due to High potent amplification mechanism, LAMP technic is sensitive,
carryover of contamination from previous LAMP reactions that lead to false
positive results (Tomita, 2008).
UDG-LAMP (Uracil DNA glycosylase ), which has recently been presented, is a
convenient and effective approach for avoiding carryover contamination in the
LAMP assay (Hsieh et al 2014).
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In the study of Zhang., 2009. detection limit of T. gondii LAMP assay with the
primers is 1 pg/μL of T. gondii DNA.
Lin et al, (2012), detection limit is 1 tachyzoite/reaction based on RE gene target.
Fallahi et al.(2015), 0.1 and 1 tachyzoite/reaction based on RE and B1 gene
Lau et al.(2010), 0.1 tachyzoite/reaction based on B1 target gene.
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Reischl et al, (2003), showed that amplification of a sequence of the T.gondii RE is at
least 10 time more sensitive than B1 gene.
RE, B1 and other Gene targets . . .
S.cassaing et al, (2006), compared the sensitives of two real time PCR assay based on RE
and B1 gene and reported RE target was more sensitive for all biological samples.
Hierl et al, (2004), applied real time PCR assays for detection of T. gondii in
immunocompromised patients and reported that RE target was more sensitive than B1
gen for toxoplasmosis detection and had the lower false negative results
Cardona et al. (2011), used two taqman real time PCR assays (RE & B1) for detection of
T. gondii in blood samples of HIV positive patients, RE target has the lower efficiency
than the B1 gene but the detection limit was same
Fallahi et al., (2013) used Nested PCR with RE and B1 gene targets to diagnosis of
toxoplasmosis in blood samples from children with leukemia. The results indicate that an
RE-based nested PCR assay is more sensitive than B1.
German Bou et al., evaluated the conventional PCR for detection of T. gondii in
aqueous humor samples compared to blood samples in immunocompetent
patients with OT and showed that the results were positive in
8 and 7 of the 15 blood and aqueous humor samples.
In Iran, Norouzi et al (2016) has shown that all seropositive (IgG positive) blood
samples have also been positive by using PCR. These studies indicate that the
blood sample can be a good alternative to aqueous humor samples that are very
high-risk.
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Sampling from Blood . . .
Bourdin et al (2018) reported a low sensitivity of 4.1% in detection of T. gondii
by using PCR on peripheral blood in OT patients.
Steeples et al., (2016) Used Real-time PCR on 529 bp repeat element for the
diagnosis of atypical ocular toxoplasmosis and revealed that real-time PCR assay
described is sensitive in diagnosis of OT.
Sugita et al., (2011) compared conventional PCR and Real Time PCR for OT
from ocular fluid samples. The results revealed that all 15 patients were negative
by Conventional PCR and 13/15 patients were positive by Real Time PCR.
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The Importance of correctly diagnosis
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