Detection and Survival of Toxoplasma gondii in Milk and Cheese from Experimentally Infected Goats

Abstract

The consumption of unpasteurized goat cheese and goat's milk has been suggested as a risk factor for toxoplasmosis in humans. In the present study, detection and survival of Toxoplasma gondii in milk and cheese was studied by bioassay in mice (milk) and in cats (cheese). Eight goats were inoculated orally with 300 to 10,000 oocysts of T. gondii strain TgGoatUS26. Milk samples were collected daily up to 30 days postinoculation and bioassayed in mice and cats. For mouse bioassay, 50 ml of milk samples were centrifuged, and the sediment was inoculated subcutaneously into mice. Mice were tested for T. gondii infection by seroconversion and by the demonstration of parasites. By mouse bioassay, T. gondii was detected in milk from all eight goats. The T. gondii excretion in milk was intermittent. For cat bioassay, 400 ml (100 ml or more from each goat) of milk from four goats from 6 to 27 days postinoculation were pooled daily, and cheese was made using rennin. Ten grams of cheese was fed daily to four cats, and cat feces were examined for oocyst shedding. One cat fed cheese shed oocysts 7 to 11 days after consuming cheese. Attempts were made to detect T. gondii DNA in milk of four goats; T. gondii was detected by PCR more consistently, but there was no correlation between detection of viable T. gondii by bioassay in mice and T. gondii DNA by PCR. Results indicate that T. gondii can be excreted in goat's milk and can survive in fresh cheese made by cold-enzyme treatment. To prevent transmission to humans or animals, milk should not be consumed raw. Raw fresh goat cheese made by cold-enzyme treatment of unpasteurized milk also should not be consumed.

Experimental studies on Toxoplasma gondii in the main livestock species (GP/EFSA/BIOHAZ/2013/01) Final report

“…Moreover, goats are considered important sources of human infection, especially for ethnic groups that commonly consume goat products (Tenter et al, 2000). Tissue cysts of T. gondii are responsible for infections via meat (Jones et al, 2012), and T. gondii tachyzoites can be excreted in goat's milk and can survive the raw fresh cheesemaking process (Dubey et al, 2014). Infections due to the consumption of raw goat's milk have been reported (Sacks et al, 1982).…”

Seroprevalence of Toxoplasma gondii infection in goats from the south-west region of Poland and the detection of T. gondii DNA in goat milk

“…Therefore, the possibility of acquiring infection by ingesting unpasteurised goat milk should be taken into consideration (Mancianti et al 2013, Dubey et al 2014. In fact, cases of clinical toxoplasmosis have been reported in humans after drinking unpasteurised goat's milk (Dubey et al 2014).…”

Prevalence of Toxoplasma gondii infection in the dairy goat population from an organic farm

“…W zależności od dawki zakaźnej okres wydalania pasożyta trwał od 8-13 do 27-30 dni po zarażeniu (8).…”

“…wykazali eksperymentalnie, że w temperaturze 4°C tachyzoity mogą pozostać żywotne w mleku kozim przez 3-7 dni (24). W innych badaniach eksperymentalnych wykazano, że pasożyt może przetrwać enzymatyczny proces wytwarzania sera z mleka koziego (8). Natomiast autorzy badający żywotność toksoplazm w mleku krowim stwierdzili, że ser wytworzony z mleka, do którego dodano wyizolowane cysty, mógł być źródłem T. gondii dla myszy w czasie dziesięciodniowego okresu przechowywania w temperaturze 4°C (8,12).…”