DISCUSSION
This study provides crucial insights into the zoonotic transmission cycle of leptospirosis in the Muheza District. The detection of leptospirosis in both livestock and humans indicates that agricultural and livestock practices contribute to the endemicity of the disease. The high seroprevalence in rodents, particularly Rattus rattus , underscores their role as a significant reservoir, while cattle likely act as incidental hosts, furthering the transmission to humans. (Schoonman & Swai, 2009, 2010; Swai & Schoonman, 2012a; Motto et al ., 2023;).
In the present study, the seroprevalence of antibody-specific leptospiral antigens among humans, rodents, and cattle was examined by using MAT as the reference serological method (Niloofa et al., 2015). The overall seroprevalence in rodents, humans, and cattle was 5.97%, 13.13% and 12.5% respectively. The difference could be due to the previous exposure to prophylactic use of antibiotics such as amoxicillin and ampicillin to treat dry cough and the use of doxycycline to treat stomach pain, explicitly patients attending hospitals within the study locality which acts as an antibacterial lowering prevalence of leptospirosis.
These findings revealed that the Rattus rattus is a potential reservoir of leptospirosis in Muheza district, as evidenced by the high infection rate among the rodents collected from various habitat types within study sites. This can be attributed to the high population in the area. But also, the fact that the species cohabits with humans and cattle, as it is mostly found in houses and peri-domestic could be another reason for being a potential reservoir of leptospirosis. Comparison of the seroprevalence of Leptospira serovars among rodent species showed statistical differences for habitat types and locations. The current finding resembles other studies conducted elsewhere in Tanzania, which also, unveiled the existence of leptospiral antibodies in Rattus rattus ( Katakweba et al., 2012; Assenga et al., 2015; Mgode et al., 2019; Motto et al., 2021; Mlowe et al., 2023) . Moreover, in rodents, the predominant serovar was Sokoine at 3.48% (n=7). The predominant of the serovar Sokoine in rodents may be attributed to their potential role as a source of leptospiral infection in humans and animals.
The variation in seroprevalence among different species and habitat types highlights the need for targeted interventions based on ecological and occupational factors. The finding that farmers are at the highest risk reinforces the importance of occupational health measures, such as protective clothing and improved hygiene practices, to reduce exposure. (Nthiwa et al., 2019). This is in line with other previous studies that have highlighted farmers as being the highest risk groups for leptospirosis in parts of Tanzania and elsewhere (Schoonman & Swai, 2009; Hashemi et al ., 2021; Maze et al ., 2023). Other researchers highlighted various groups including dog keepers (Msemwa et al., 2021), livestock keepers (Motto et al., 2023), fishing communities (Mgode et al., 2019), slaughter pigs (Ngugi et al., 2019), slaughtered cattle (Swai & Schoonman, 2012b) as well as miners and sewage workers (Hashemi et al., 2021) being the highest risk group for contracting leptospirosis.
Interestingly, in humans, the predominant serovar was Grippotyphosa followed by Sokoine. Other prevalent serovars included Hebdomadis, Pomona, and Lora, with none detected in Canicola. The predominant of Grippotyphosa in humans could be due to the high contact rate between humans and cattle within the study locality, especially during the milking stage. The predominance of Grippotyphosa in cattle may be due to their role as maintenance hosts for this serovar. Cattle are recognized as natural and maintenance hosts for serovar Grippotyphosa (Soareset al., 2020). (Assenga et al., 2015; Mgode et al ., 2021; Msemwa et al., 2021; Majawa et al., 2023; Mloweet al., 2023).
The study’s identification of co-agglutination between rodents, cattle, and humans for multiple serovars further emphasizes the complex dynamics of leptospirosis transmission in multi-host systems. The shared environment, particularly water sources, likely plays a key role in maintaining the infection cycle between these species. Mgode et al ., 2021; Msemwa et al., 2021; Majawa et al., 2023).
The seroprevalence data for rodents, cattle, and humans in Muheza District is consistent with other studies conducted in Tanzania, such as in Katavi, where a high prevalence was reported in humans (29.96%), and in Tanga, where bovine leptospirosis was also prevalent (Motto et al ., 2023). These results underscore the importance of considering local environmental and socio-economic factors when developing control measures.