Recent cockroach bacterial contamination trend in the human dwelling environments: A systematic review and meta-analysis

Background: Cockroaches have been compromised with the human environment posing some risks to humans. Objective: A systematic review and meta-analysis study about the bacterial contamination of cockroaches in the human dwelling environmentswere investigated. Methodology: Relevant topics about bacterial contamination of cockroaches were collected from scientific websites between January 2016 and January 2017. After a preliminary review 32 of the collected topics were selected to become part of the detailed synthesis meta-analysis review. Results: Results showed that the global mean bacterial contamination trend of cockroaches and Periplaneta americana ranged 45.0-80.0 and 55.0-75.0 %, respectively which were increased while it were 90.0-50.0 % for Blattella germanica which decreased in recent years. The global mean bacterial contamination of cockroaches, P. americana and B. germanica was also 67.9, 72.9 and 62.9 %, respectively which P. Americana had the most global mean bacterial contamination. Statistical analysis didn’t show any significant differences between any combination of bacterial contamination of the cockroaches, and P. americana and B. germanica surfaces such as totalexternal, total-internal and external-internal; any type environment of cockroaches, P. americana and B. germanica including households, hospitals and miscellaneous; any combination of bacterial contamination such as between total-total, external-external and internal-internal surfaces of the P. americana and B. germanica; and P. americana and B. germanica in combination environments of households-households, hospitals-hospitals and miscellaneous-miscellaneous (P > 0.05). Conclusions: The external and internal surfaces of any type cockroach have equal importance ofbacterial contamination and they threaten human health in the any type environment.


Materials and methods Data collection and selection
Relevant topics, papers and scientific notes about contamination of cockroaches were collected from various websites such as Google Scholar, specific scientific sites, Scopus, PubMed, Web of Science, Elsevier and Springer, as well as Science Direct, between January 2016 and January 2017. About 249 papers and scientific notes were collected from the mentioned addresses and after a preliminary review, 44 were selected to become part of the detailed synthesis review and meta-analysis.

Data meta-analysis
The papers and scientific notes about contamination of cockroaches to bacteria were read carefully and the useful subjects were extracted and sorted. Bacterial contamination of cockroaches mainly categorized into three parts including hospitals, households and miscellaneous environments. As the hospitals and households are the important human dwelling environments, the cockroach bacterial contamination categorized into two these distinct parts, while the other type of cockroach bacterial contamination was arranged in the miscellaneous part. The results summarized in the table 1.

Statistical analysis
The global bacterial contaminationt rend of cockroaches, and Periplaneta americana and Blattella germanica cockroach species were calculated and estimated by Microsoft Excel 2010. The global trend cockroach fungal contamination was drawn by clicking on graph line distribution and selecting "add trendline" option. The global cockroach fungal contamination was calculated by insertion function and selecting "average" option. Fig. 1 shows the global bacterial contamination trend of cockroaches, and Periplaneta americana and Blattella germanica cockroach species. IBM SPSS Statistics Data Editor Version 23 was used to analyze any statistical analysis of the data. Onesample Kolmogorov-Smirnov testwas used to check the normality of the data distribution. After checking to make sure that the distribution of data was normal, paired-samples t-test was used to compare contamination of cockroaches between two groups, while ANOVA was used to compare contamination of cockroaches among more than two groups including the hospital, householdand miscellaneous environments for any significant difference. Table 2 shows statistical analysis of bacterial contamination of cockroaches, and Periplaneta americana and Blattella germanica cockroach species.

Cockroach global mean bacterial contamination
The global mean bacterial contamination of cockroaches was 67.9 %.The global mean bacterial contamination of P. americana cockroaches was 72.9 %.The global mean contamination of B. germanica cockroaches was 62.9 % (Fig. 1).

Cockroach body part bacterial contamination analysis
There was no any significant differences between any combination of bacterial contamination such as between total-external, total-internal and externalinternal surfaces of cockroaches, and P.americana and B.germanica cockroach species (P > 0.05) except between total-internal and external internal-internal surfaces of B. germanica cockroaches (P=0.031).
There was also no any significant differences between any combination of bacterial contamination such as between total-total, external-external and internal-internal surfaces of the P. americana and B. germanica cockroach species (P > 0.05) ( Table 2).

Discussion
Like pediculosis, scabies, myiasis and tick-borne  (Fig. 1). The global mean bacterial contamination of cockroaches, American and German cockroach species was also 67.9, 72.9 and 62.9 %, respectively which American cockroach species (72.9 %) had the most global mean bacterial contamination. Statistical analysis didn't show any significant differences between bacterial contamination of cockroaches, and American and German cockroach species (P > 0.05) ( Table 2) suggests that the cockroaches, and American and German cockroach species have the same importance of bacterial contamination. Statistical analysis didn't show any significant differences between any combination of bacterial contamination such as between total-external, total-internal and external-internal surfaces of the cockroaches, and American and German cockroach species (P > 0.05) except between total-internal and external internal-internal surfaces of German cockroach species (P = 0.031). There was no any significant differences between any combination of bacterial contamination such as between totaltotal, external-external and internal-internal surfaces of the American and German cockroach species (P > 0.05) ( Table 2). These facts suggest that the external-internal, external and internal surfaces of cockroaches, and American and German cockroaches have equal importance of bacterial contamination. Statistical analysis didn't show any significant differences between bacterial contamination of any type environment (such as households, hospitals and miscellaneous) of cockroaches, American and German cockroache species (P > 0.05) ( Table 2). Statistical analysis also didn't show any significant differences between bacterial contamination of American and German cockroach species in combination environments of householdshouseholds, hospitals-hospitals and miscellaneousmiscellaneous (P > 0.05) ( Table 2). These facts suggest that the cockroaches, andAmerican and German cockroach species threaten human health in the any type environment. Although a variety of disease agents can be currently spread by cockroaches, while it is possible to determine cockroach transmitting ability of the disease agents that they are not capable to transmit them by artificially contamination of cockroaches [43][44] .

Conclusion
Cockroaches have been compromised with the human life environments. As cockroaches are being harbor of pathogenic organisms and move freely from areas within hospitals, they are considered as transmitter of nosocomial infection at hospital environments. A systematic meta-analysis review about cockroach bacterial contamination in the human dwelling environments was investigated. The results indicate that the global mean bacterial contamination trend of cockroaches were increased in recent years. The global mean bacterial contamination of cockroaches, P. americana and B. germanica cockroach species was 67.9, 72.9 and 62.9 %, respectively which P. americana (72.9 %) had the most global mean bacterial contamination. Statistical analysis didn't show any significant differences between cockroaches, and P. americana and B. germanica cockroach surfacesand any environment type (such as households, hospitals and miscellaneous) of cockroach bacterial contamination (P > 0.05). These facts suggest that external and internal surfaces of cockroaches, and P. americana and B. germanica cockroach species have equal importance of bacterial contamination and they threaten human health in the any type environment.

Acknowledgments
This work did not receive any technical or financial support from any institution and was done by the author at his own personal expense.

Conflict of interest: None
Author's contribution: Data gathering and idea owner of this study, Study design, Data gathering, Writing and submitting manuscript: Editing and approval of final draft, all events have done by Hassan Nasirian