This year, a few unlucky herds have been infected with an algae mastitis cause from the organism Prototheca. Prototheca are microscopic algae that are found all over the world. 

Despite the organism being widespread in the environment, the incidence of prototheca mastitis in New Zealand is very low.  Most cases involve one or two animals, with the appropriate action being to cull the infected cow.  

Both environmental and contagious transmission of prototheca can occur. 

The original source of infection is likely to be environmental as prototheca can be found in soil, waterways, faeces or any wet organic material. The prototheca can survive from weeks to months and can be shed in the faeces of cows with or without mastitis. 

Once cows are infected then the algae can spread from cow to cow through the milking process. Poor teat disinfection and/or a high level of teat end damage may contribute to the spread of infection. 

Prototheca can cause both clinical and subclinical mastitis with most cases becoming chronic, subclinical infections because the self-cure rate is very low. The infection will result in an elevated somatic cell count but in some individuals this elevation can be mild and progress slowly. 

Milk production tends to decrease but it may remain constant in some cows. Prototheca can survive in milk secretions over the dry period and reappear in colostrum in the next season. 

To diagnose prototheca we need to get a milk sample for culture. This is what they look like under the microcope! 

Prototheca algae

In the spring of 2016 two dairy herds in the Waikato were identified with multiple cows infected with prototheca. The exact source of the infection has not been established. 

In one herd, to date 203 out of 700 cows have been diagnosed positive to prototheca. The somatic cell count of prototheca positive cows ranged from 62,000 to 4,600,000!

Another herd to date, has had over 1700 samples taken, and 462 cows have cultured positive for prototheca.  

Take home message:
Milk culturing is the best way to diagnose what is happening in your herd, as sometimes it may be a little strange! 

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