During the present study, the prevalence of intestinal parasites was evaluated in buffalo calves aged between 2 and 11 weeks in northwestern Romania. Three protozoan parasites (Eimeria spp., Cryptosporidium spp., and G. duodenalis) and two nematodes (T. vitulorum and S. papillosus) were identified. These GIT parasites are the most common found in buffalo calves worldwide 11, 12.
In the present study, Eimeria spp. was the most prevalent GIT parasite and detected in 84.2% of buffalo claves. This ubiquitous protozoan has a worldwide dispersal in water buffaloes which could be infected with at least 12 Eimeria species, of them 11 are of cattle origin 13. So far, E. bareillyi is the only buffalo-specific species, non-transmissible to cattle, and is highly pathogenic to young calves 14. This is the first report of E. bareillyi oocysts in buffalo calves from Romania; however, infections were subclinical, and the oocysts were detected in all age groups. E. bareillyi infections have been reported worldwide (Dubey, 2018) including 2 reports from Europe; in Italy 15, 16 and the Netherlands 17. The prepatent period is 12–15 days after experimental infection with 350000-15000000 E. bareillyi oocysts 14. In natural infections, oocysts were detected at 13 days of age 18; however, oocysts from other species (e.g. E. bovis, E. ellipsoidalis, E. auburnensis and E. zuernii) were noticed as early as 2–7 days of age 19. Therefore, a study on buffalo calves from E. bareillyi-infected farm and involving daily examination of fecal samples from the 1st day of birth is required to detect whether E. bareillyi oocysts are excreted in the first week of life.
The second most found parasite in the present study is T. vitulorum (36.8%), which is frequently found in tropical and sub-tropical regions 20, 21, and less often in temperate climates as in Europe. This parasite can cause significant morbidity and mortalities in calves. We noticed T. vitulorum eggs, but not the mature worms, in feces of the examined calves of all age groups. T. vitulorum larvae are passed in great numbers in the buffalo cows colostrum 2–5 days post-calving, worms are matured in the intestine of the calves by 10 days of age and eggs are passed in feces approximately at the 3rd week of life and then adult worms are expelled from the intestine by the 5th month of age 22, 23. In Europe, this nematode parasite was reported in the latest years at the farm level in cattle 24–29 and bisons 30. In western Romania, the parasite was detected in 0.3% of 303 fceal samples from cattle 31.
Additionally, S. papillosus eggs were found in 15.8% of the examined buffalo-calves in the present study, and the prevalence increased with the age. A lower prevalence (3.1%) was detected in water buffaloes (adults, heifer/steers and calves) from Italy 32. However, higher values have been reported worldwide: 28.5% in India (Jyoti et al., 2014); 59.4% in Mexico (Ojeda-Robertos et al., 2017) and 87% in 3 months old calves in Sri Lanka 33–35. Despite Strongyloides species infects all age groups, clinical signs such as diarrhea and malnutrition are frequently seen in young animals 36. Sudden deaths were reported in naturally and experimentally infected calves and the dead calves harbored an EPG value between 52000 and 411000 37. Strongyloides-infected calves from our study presented low EPG (under 1000). Considering the high pathogenicity of the parasite, calves with high EPG (> 10000) should be treated 36.
Our results demonstrate Cryptosporidium infections in 4 (10.5%) buffalo calves; this prevalence is comparable to earlier studies worldwide 4, 5, 7. However, our prevalence is much lower than that from buffalo-calves (2–4 months) from Egypt (40.0%) and Brazil (54.1%) 6, 38. Compared to cattle (25.19–28.52%) from the country of study (Romania), the obtained prevalence in buffalo calves is lower 39, 40. DNA from 3 of the four Cryptosporidium isolates was successfully amplified and sequenced, and the obtained sequences revealedC. ryanae infection in 2 samples, whereas the 3rd isolate was unidentified but related genetically to the bovine C. ryanae and C. bovis as well as the ovine C. xiaoi. C ryanae is the most common Cryptosporidium species reported worldwide in buffaloes 41, 42, but also C. parvum, and C. bovis 41–44. In Romania, C. parvum was reported in cattle, and as the predominant species in lambs 40, 45, 46. Our results cannot deny the role of buffaloes in the transmission cycle of C. parvum due to the limited number of tested samples and sequenced isolates.
Moreover, a single sample was positive for G. duodenalis infection, and sequence analysis revealed the occurrence of the assemblage E. This assemblage is non zoonotic and commonly circulates among different farm animals including cattle, sheep, goat and horses 47, and has been detected together with the assemblage A in buffaloes from Italy (Caccio et al., 2007), Australia 4, 48, 49 Egypt (Helmy et al., 2013).
Generally, buffaloes are considered robust species and therefore more resistant to diseases compared with cattle. However, this study pointed out that pre-weaned buffalo-calves are exposed to early infection with pathogenic E. bareillyi, and other Eimeria species, and to the infection with T. vitulorum. Moreover, the infection risk for T. vitulorum increased when in the same barn were more than two buffaloes. Multiple infections, and currently parasitizing the same region of intestine, can adversely affect the growth of buffaloes. These data pointed out the need for early antiparasitic treatments for coccidiosis and toxocarosis in buffalo-calves. Buffalo-calves are not a source of zoonotic C. parvum and G. duodenalis in our area.