Under the Microscope: Protozoa

As part of the University of Dundee Museums' current exhibition, Uncertain Territories - Women and Nature, a selection of microscope slides from the collection have been enlarged and digitised.

The exhibition explores the role of women artists and scientists in helping us understand the natural world. Among them is Doris Mackinnon (1883-1956).

Born in Scotland, Mackinnon studied botany and geology at Aberdeen University, achieving her doctorate in 1914, before becoming a lecturer at the University of Dundee (then University College, Dundee and part of the University of St Andrews) in 1916. In 1919, Mackinnon joined King's College London as a lecturer and became Chair of Zoology in 1927- the first female Chair at the college.

During WW1 Mackinnon worked in military hospitals in Britain, researching and helping to diagnose amoebic dysentery (an infection of the intestines caused by the protozoan parasite Entamoeba histolytica). Parasitic protozoa would become the focus of her research over the next 30 years of her career.

What are Protozoa?

Protozoa are single-celled organisms. They can be either parasitic or free-living in nature. Some of them are responsible for common diseases such as giardia, toxoplasmosis, leishmania and malaria.

Protozoa are able to multiply in humans which allows serious infections to develop from a single organism. They are transmitted from human to human via the faecal-oral route or through an insect vector such as the mosquito or sandfly.

Below are some of the slides which have been digitised as part of the Uncertain Territories exhibition and their associated health impacts.

Plasmodium - Malaria

Image: Malaria

Malaria is one of the most well-known protozoan diseases. It is caused by the protozoa of the genus Plasmodium and passed to humans through the bite of an infected female mosquito. It is diagnosed by identifying the protozoa in a sample of the patient's blood.

Symptoms of malaria may include fever, chills, sweating, muscle aches as well as nausea, vomiting and diarrhoea. If left untreated, the infection can become serve causing kidney failure, seizures, mental confusion, coma and even death.

Although medications and insecticides make malaria treatable and preventable, lack of funding means the disease remains common and deadly in many parts of the world.

Coccidia - Coccodiosis

Image: Coccidia

Coccidia are tiny-celled parasites that live and reproduce inside animal cells. Infection with these parasites is known as coccidiosis and it can occur in many mammals as well as some species of birds, fish and reptiles. It is particularly common and of concern in poultry farming where it is the target of costly prevention measures.

There is a difference between infection with coccidia, which is common, and coccidiosis itself which is infrequent. For example, many rabbits will be infected by coccidia at least once in their lifetime but will not go on to develop disease.

Humans can become infected by consuming undercooked meat or contact with infected cat faeces.

Noctiluca - Red Tides

Image: Noctiluca

Noctiluca is a type of marina dinoflagellate and one of the most commonly occurring bioluminescent organisms in coastal regions.

During a 'bloom' (population increase) it produces an effect which historically has been called 'sea sparkle' or 'burning of the sea' by sailors. Whilst glowing at night, in the daytime the bloom forms a thick scum across the sea surface that is red.

Although not thought to produce harmful toxins itself, this ride-tide effect is associated with massive fish mortalities and harm to other marine species, affecting yields in fisheries and polluting the water. It can also cause skin and eye irritation to swimmers. Therefore swimming in a red tide is not advised. This example shows an indirect effect of protozoa on human health.

Three types of protozoa have been shown here with consequences for human, animal and environmental health. With over 50,000 species having been described and the presence of protozoa found in almost every possible habitat, there is plenty still left to discover about these microscopic organisms.

The University of Dundee Museums exhibition Uncertain Territories: Women and Nature is free to visit Monday to Saturday until 1st April 2023. You can find the exhibition at the Tower Foyer Gallery, Dundee.