Toxoplasma, Entamoeba histolytica, Amoebic meningoencephalitis & keratitis

Toxoplasmosis 

Relevant manifestations to consider further:

  • congenital – diagnosis – excellent recent guide 
  • reactivation in an immunocompromised (deficient cell-mediated immunity ) patient  such as someone with advanced HIV – then cerebral abscess (may be multiple), retinitis or pneumonitis (similar picture to pneumocystis) occur – direct tissue demonstration of tachyzoites required generally (PCR also possible).   Presumptive diagnosis usually made in HIV patient with cerebral abscess, usually after checking to confirm IgG seropositivity – therapeutic trial of antibiotic therapy then occurs – if no response then other differentials become more relevant – e.g. cerebral lymphoma.

Seroprevalence of anti-Toxoplasma gondii antibodies in HIV/AIDS patients and healthy blood donors at the Port Moresby General Hospital, Papua New Guinea.P N G Med J. 2012 Mar-Dec;55(1-4):88-93.   301 patients (181 HIV positive); overall antibody prevalence rate of 53% in the population and a significantly higher infection rate amongst HIV-positive patients.

Entamoeba histolytica

Note that if someone is a carrier (passes cysts of Entamoeba), then if they develop diarrhoea from some other cause, the cysts will form trophozoites – this does NOT mean the patient has amoebic dysentery!

Amoebic meningoencephalitis and keratitis

Primary amoebic meningoencephalitis in North Queensland: the paediatric experience. Med J Aust. 2016 Oct 3;205(7):325-8. Primary amoebic meningoencephalitis (PAM) is a fulminant, diffuse haemorrhagic meningoencephalitis caused by Naegleria fowleri, with an almost invariably fatal outcome. In Australia and the developed world, PAM remains a rare disease, although it is very likely that large numbers of cases go undetected in developing countries. N. fowleri is a thermophilic, free-living amoeba with a worldwide distribution. It is acquired when contaminated fresh water is flushed into the nose and penetrates the central nervous system via the cribriform plate. Clinical features are similar to those of bacterial meningitis, but it does not respond to standard therapy and rapid progression to death occurs in most cases. Some survivors have been reported; these patients received early treatment with amphotericin B in combination with a variety of other medications. Our review describes the local and worldwide experience of this disease and its clinical features, and discusses the associated diagnostic challenges. We hope that by detailing the local response to a recent case, and the outcomes of our public health campaign, we can improve the knowledge of this rare disease for doctors working in rural and remote Australia.

Primary amoebic meningoencephalitis in the Western Province. P N G Med J. 1991 Jun;34(2):87-9.  Six cases of primary amoebic meningoencephalitis were diagnosed and treated at the Balimo Health Centre between December 1986 and September 1988. This disease has not previously been reported in Papua New Guinea although from information derived from other studies it should be occurring in the lowlands of Papua New Guinea from time to time. Although less than optimum treatment was given to the early cases the case fatality rate in the series was only 66%. This compares very favorably with a case fatality rate of nearly 100% from other studies. Early diagnosis and prompt treatment should help to reduce mortality.

Strategies for the prevention of contact lens-related Acanthamoeba keratitis.  Ophthalmic Physiol Opt. 2016 Mar;36(2):77-92.  Acanthamoeba keratitis is a severe, often sight threatening, corneal infection which in Western countries is predominantly seen in daily wear of contact lenses. This review aims to summarise the pathobiology and epidemiology of contact lens-related Acanthamoeba keratitis, and to present strategies for prevention, particularly with respect to modifiable risk factors in contact lens wear.

About mdjkf

Microbiologist and Infectious Diseases Physician
This entry was posted in Module - Parasitology, Parasitology and tagged , , . Bookmark the permalink.

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