Goats could potentially transmit a dangerous parasite, Toxoplasma gondii, in their semen, according to research by Flaviana Wanderley and colleagues in Brazil. Well…who cares? Why should scientists devote research dollars and time to purposely giving goats STDs, just to see if they can?
Like with so many other apparently bizarre research projects, the answer is: it’s the economy, stupid!
Goat farming is very important in many countries, including Brazil and India. Goats are reared for both meat and milk, and can be much more economical to raise than sheep or cows. As of 2005, there were 9.1 million goats being raised in Brazil–that’s more than the population of Switzerland! The parasite Toxoplasma gondii is extremely harmful to goats, causing congenital diseases and even abortions. So, you can see how preventing the transmission of this parasite in their livestock might be of importance to goat farmers.
Previous research found that Toxoplasma can be found in goat semen. They also found that experimental insemination of female goats with artificially contaminated semen can transmit the disease, called toxoplasmosis. But only two strains (G1 and G2) of Toxoplasma have been tested so far in this way. The G1 strain was able to infect about a third of females via the semen. G2 infected 100% of females. G2 infections also resulted in “embryonic resorption” (spontaneous abortion). The third strain, G3, was tested in the current study.
Let’s take a step back for a second to appreciate how this experiment is actually carried out. The paper only says that semen “was provided by” a male with a history of fertility, but there are two predominate ways that semen is collected in goats (and many other animals): artificial vagina and electroejaculation. The artificial vagina method involves getting a male to mate with a mock female that has a, well, artificial vagina. Then you just collect the sample afterwards. Electroejaculation, on the other hand, is generally done with an anesthetized male. An electric current is applied, usually rectally, to the prostate and voilà! Semen sample.
The parasites used for the experiment were isolated from an outbreak of abortions (never thought I’d see those words together in print. They used this phrase in the paper, too) in Guarapuava, Brazil in 2008. Goat abortions, obviously. The isolated parasites were then grown in the lab, using mice as the incubators.
Finally, parasites were mixed with semen in the correct concentrations and administered to the female goats. Vaginally. So far, none of this sounds like the kind of day you want to tell your mom about at the dinner table. To guard against false positives skewing the data, the researchers also inseminated a separate group of goats with semen (from the same male) that didn’t have any parasites added to it.
In the experimental group, those females that received infected semen, 3 out of 5 had detectable parasite DNA in their blood one week after infection. There was no detectable parasite DNA in the control group. 4 of the 5 females in the experimental group had abortions by the 49th day after infection.
This particular study was different from the previous ones, in that it tested the effect of infection at the same time as fertilization. Earlier studies had infected females that were already pregnant, and showed that it caused those females to abort or reabsorb the embryos. This study confirms that toxoplasmosis is harmful to female goats’ reproduction. It also shows that the third strain (G3) of Toxoplasma gondii is able to be transmitted through the semen at a high rate.
Still, no one has yet shown for sure that Toxoplasma gondii in the semen of an infected male has been the route of infection for a mated female–but it’s pretty likely given these results.
Unfortunately, I doubt that the tools for testing a male’s semen before allowing him to mate are available to most goat farmers in the world. Making these tests available to farmers, possibly through some kind of government assistance, would probably have a significant impact on the economy in countries where goat herding is important.
Wanderley F, Porto WJ, Câmara D, Cruz NL, Feitosa BC, Freire R, Moraes E, & Mota R (2013). EXPERIMENTAL VAGINAL INFECTION OF GOATS WITH SEMEN CONTAMINATED WITH THE “CPG” STRAIN OF Toxoplasma gondii. The Journal of parasitology PMID: 23391103