RESUMEN
Sixty suspected protozoan oocysts were demonstrated from 260 fecal samples collected from water buffaloes aged one month to seven years old with clinical signs of diarrhea in four provinces in the Philippines after conventional methods of isolation, sporulation, morphological characteristics and Kinyoun Acid Fast Staining techniques. The recovered protozoan oocysts were subjected to molecular analysis. Amplification of DNA extracted from recovered Eimeria oocysts using universal primers for the ITS-1 region of 18S rRNA revealed PCR products with 348 bp size demonstrated by samples collected from Benguet, La Union and Nueva Ecija provinces in the Philippines while DNA extracted from oocysts of suspected Cryptosporidium spp. samples that applied primers for the SSU of 18S rRNA registered PCR products but no genes were amplified from diarrheic water buffaloes from these provinces. Alignment of the DNA sequences of the suspected Eimeria and Cryptosporidium species revealed sequences for three isolates of Buxtonella sulcata with product lengths that varied from 235 to 252 bp. This is an initial observation on the involvement of B. sulcata in diarrhea condition of water buffaloes in the Philippines. Phylogenetic analysis of the three local isolates of B. sulcata revealed no similarity with other protozoan constructed according to Neighbor-Joining method.