{"id":924761,"date":"2026-10-11T23:36:15","date_gmt":"2026-10-11T23:36:15","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/924761\/"},"modified":"2026-10-11T23:36:15","modified_gmt":"2026-10-11T23:36:15","slug":"toxoplasmosis-a-common-but-neglected-infectious-disease","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/924761\/","title":{"rendered":"Toxoplasmosis : A common but neglected infectious disease"},"content":{"rendered":"

Toxoplasmosis is an infectious disease caused by the parasite, Toxoplasma gondii.<\/a> Ocular involvement is the biggest clinical problem, characterised by recurrent attacks of retinitis that may extend to involve tissues abutting the retina \u2014 the choroid and the vitreous. Toxoplasmosis cannot be cured, but it is preventable and controllable.<\/p>\n

There has been limited recognition of the substantial health burden of toxoplasmosis. We recently led an\u00a0international call-to-action<\/a>, highlighting that toxoplasmosis meets the World Health Organization criteria for a neglected tropical disease, although it has not been formally recognised.\u00a0Recognition would identify toxoplasmosis for attention by the health sector and government, and open up funding streams for research on vaccines, better diagnostics, and curative drugs, plus support from the WHO to implement public health and One Health programs.\u00a0<\/p>\n

Common in Australia<\/p>\n

Approximately 1 in 150 Australians have ocular toxoplasmosis.<\/a> The disease often presents in healthy adults and can be vision-threatening: approximately\u00a050% of patients<\/a> treated for ocular toxoplasmosis suffer permanent vision impairment in the affected eye, and 1 in 5 are blinded in that eye. Ocular toxoplasmosis can be more aggressive when it occurs in people who have\u00a0immunodeficiencies<\/a> or are immunocompromised.\u00a0Congenital toxoplasmosis<\/a> is a rare, but devastating form that can be disseminated and even result in loss of a pregnancy.<\/p>\n

Mechanisms of infection<\/p>\n

T. gondii<\/a> is a single-celled parasite and\u00a0a close relative of the Plasmodium species that cause malaria. It can infect any\u00a0mammal or bird<\/a>, and an estimated one-third of the global human population carries it.\u00a0<\/p>\n

The parasite replicates sexually in the gut of the cat, its primary host. It is passed in cat faeces as highly infective sporozoites, packaged as hardy oocysts. Thus, T. gondii may contaminate the grazing areas of livestock. It lodges in the muscles of infected livestock as dormant encysted bradyzoites, and when the animals are slaughtered for meat, cuts may contain the parasite.<\/p>\n

Humans can become\u00a0infected<\/a> with T. gondii by several routes. Many of us are infected by eating\u00a0meat<\/a> raw or undercooked. Contamination of\u00a0Aussie lamb<\/a> was documented in a study that involved testing mince purchased at a supermarket 3-weekly for six months: conservatively measured,\u00a043% of mince purchases contained parasite DNA<\/a> by polymerase chain reaction (PCR). Some health advisories state that red meat is safely eaten after searing the surface, but cooking to an internal temperature of\u00a066\u00b0C is required to kill T. gondii.<\/p>\n

T. gondii is also contracted by eating unwashed produce harvested from cat-soiled gardens. Congenital infections may occur if a woman is infected for the first time during pregnancy, when she lacks secondary immunity.\u00a0<\/p>\n

The parasite converts to actively replicating tachyzoites in the intestine and moves into the blood stream, often taxiing in leukocytes. It crosses from the blood into the tissues, with a particular affinity for the\u00a0retina<\/a> that is likely related\u00a0to specific molecular interactions with the local vascular endothelium.\u00a0<\/p>\n

Within the retina, T. gondii replicates within and lyses retinal cells, and triggers a robust immune response. But, under threat from the immune system, tachyzoites soon convert to bradyzoites, which are invisible to leucocytes. Conversion back to tachyzoites at some later date triggers a recurrent attack of retinitis. In essence, the activity cycle of ocular toxoplasmosis is akin to that of herpetic stomatitis.\u00a0<\/p>\n

Making the diagnosis<\/p>\n

The initial infection with T. gondii is often asymptomatic or it passes as a mild influenza. There is no gender predilection. Common symptoms of a new attack of ocular toxoplasmosis are sudden onset of floaters and altered vision in one eye.\u00a0<\/p>\n

In over\u00a090% of patients<\/a>, making the diagnosis of ocular toxoplasmosis is straightforward because of the characteristic lesion: a single focus of fluffy white retinitis adjacent to a pigmented scar (Figure 1), often associated with substantial inflammation in the vitreous. Ophthalmologists call this presentation \u2018headlight in the fog\u2019. Generally, T. gondii serology is not needed, although it may be ordered as a reassurance of the diagnosis.\u00a0<\/p>\n

In a small percentage of patients, the presentation is atypical, for example, multiple active retinal lesions, no retinal scar, and neuroretinitis. In these situations,\u00a0aqueous may be sampled<\/a> by anterior chamber paracentesis for testing by PCR for T. gondii DNA.\u00a0<\/p>\n

Treating ocular toxoplasmosis<\/p>\n

Although toxoplasmic retinitis\u00a0resolves spontaneously<\/a> over approximately two months, ophthalmologists usually recommend treatment. This is particularly the case when the retinitis is located near the macula, as even a small area of retinal necrosis may irreversibly decrease the visual acuity. Moreover, the patient\u2019s own inflammatory response may cause complications that also can impact the vision, such as glaucoma, macular epiretinal membrane, and retinal detachment.\u00a0<\/p>\n

A combination of\u00a0anti-microbial and anti-inflammatory drugs<\/a> is commonly prescribed for healthy adults, often an extended course of trimethoprim-sulphamethoxazole and a limited course of prednisolone. Locally delivered treatment is occasionally used, involving intravitreal injections of clindamycin and dexamethasone. For those cases in which another flare could result in progressive vision loss, low-dose\u00a0trimethoprim-sulphamethoxazole<\/a> may be given. Treatment of immunocompromised or congenitally infected persons requires\u00a0intensive anti-microbial drug regimens<\/a>.\u00a0<\/p>\n

Prevention<\/p>\n

Toxoplasmosis is\u00a0not an unavoidable consequence<\/a> of our interactions with animals. Globally, various community-based measures can prevent or control T. gondii infections, including water treatment, management of stray cats, farming practices to protect livestock areas, pregnancy screening programs, and health systems that give access to drugs and low vision support. Additionally, there are simple precautions any individual can take to protect themselves against infection (Table 1).<\/p>\n

Table 1: Individual actions that prevent against infection with Toxoplasma gondiiCook meat to internal temperature of 66 \u00b0C. Don\u2019t eat meat rare unless it has been frozen.\u00a0Wash fresh vegetables and fruits.Don\u2019t drink from rivers streams. If local water is not treated, use bottled water or filter water.Garden with gloves.Change cat litter regularly, with gloves, into sealed bag, and dispose of bag into rubbish. Pass job to someone else if pregnant.Wash hands after removing gloves.<\/p>\n

Professor Justine Smith is an ophthalmologist-scientist at Flinders University and Flinders Medical Centre in Adelaide, Australia. Her clinical specialty is uveitis.\u00a0<\/p>\n

Associate Professor Joa\u0303o Furtado is an ophthalmologist at the\u00a0Ribeir\u00e3o Preto Medical School of the University of S\u00e3o Paulo, in Ribeir\u00e3o Preto, Brazil. He also works on contract at the World Health Organization.\u00a0<\/p>\n

The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the\u00a0MJA\u00a0or\u00a0InSight+\u00a0unless so stated.\u00a0<\/p>\n

Subscribe to the free\u00a0InSight+\u00a0weekly newsletter\u00a0here<\/a>. It is available to all readers, not just registered medical practitioners.\u00a0<\/p>\n

If you would like to submit an article for consideration, send a Word version to\u00a0mjainsight-editor@ampco.com.au<\/a>.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"Toxoplasmosis is an infectious disease caused by the parasite, Toxoplasma gondii. Ocular involvement is the biggest clinical problem,…\n","protected":false},"author":2,"featured_media":924762,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[64,63,137],"class_list":["post-924761","post","type-post","status-publish","format-standard","has-post-thumbnail","category-health","tag-au","tag-australia","tag-health"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/924761","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=924761"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/924761\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/924762"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=924761"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=924761"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=924761"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}